A recording-medium binding device includes a first tooth row that includes teeth arranged in a tooth arrangement direction and a second tooth row that includes teeth, that is to be engaged with the first tooth row, and that cooperates with the first tooth row to bind recording media by pinching a batch of the recording media. In the tooth arrangement direction, the first and the second tooth rows have first and second ranges. In the first range, an engaging height is a first engaging height, and a width of an effective tooth top is a first effective tooth top width. In the second range, the engaging height is a second engaging height that is smaller than the first engaging height, and a width of an effective tooth top is a second effective tooth top width that is larger than the first effective tooth top width.

There is provided a binding member. The binding member includes: an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in side surfaces of the recesses of one toothed part, when the upper toothed part and the lower toothed part are engaged, surfaces wide in a direction parallel to the pressing direction of the toothed parts are formed so as to be provided gaps between the upper toothed part and the lower toothed part.

There is provided a binding member. The binding member includes: an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in side surfaces of the recesses of one toothed part, when the upper toothed part and the lower toothed part are engaged, surfaces wide in a direction parallel to the pressing direction of the toothed parts are formed so as to be provided gaps between the upper toothed part and the lower toothed part.

There is provided a binding member. The binding member includes: an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in side surfaces of the recesses of one toothed part, when the upper toothed part and the lower toothed part are engaged, surfaces wide in a direction parallel to the pressing direction of the toothed parts are formed so as to be provided gaps between the upper toothed part and the lower toothed part.

There is provided a binding member. The binding member includes: an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in side surfaces of the recesses of one toothed part, when the upper toothed part and the lower toothed part are engaged, surfaces wide in a direction parallel to the pressing direction of the toothed parts are formed so as to be provided gaps between the upper toothed part and the lower toothed part.

A recording-medium binding device includes a first tooth row that includes teeth arranged in a tooth arrangement direction and a second tooth row that includes teeth, that is to be engaged with the first tooth row, and that cooperates with the first tooth row to bind recording media by pinching a batch of the recording media. In the tooth arrangement direction, the first and the second tooth rows have first and second ranges. In the first range, an engaging height is a first engaging height, and a width of an effective tooth top is a first effective tooth top width. In the second range, the engaging height is a second engaging height that is smaller than the first engaging height, and a width of an effective tooth top is a second effective tooth top width that is larger than the first effective tooth top width.