An inclination controlling mechanism of a seatbelt device is provided with: a pulley that converts an advancing/retracting movement of a cable of the cable advancing/retracting mechanism; a drive gear mounted around a pivot shaft of the pulley and synchronized with rotation of the pulley; and a driven gear mounted around a pivot shaft of a sensor housing so as to move in conjunction with a rotation of the sensor housing. The drive gear and driven gear engage with each other in a condition where a rotational track surface of the drive gear and rotational track surface of the driven gear intersect at a predetermined angle. As a result, an inertial body supporting surface serving as a sensor reference plane can be accurately maintained horizontally even at an arbitrary seatback recline angle, and thus the accuracy of the acceleration sensor can be improved.

An inclination controlling mechanism of a seatbelt device is provided with: a pulley that converts an advancing/retracting movement of a cable of the cable advancing/retracting mechanism; a drive gear mounted around a pivot shaft of the pulley and synchronized with rotation of the pulley; and a driven gear mounted around a pivot shaft of a sensor housing so as to move in conjunction with a rotation of the sensor housing. The drive gear and driven gear engage with each other in a condition where a rotational track surface of the drive gear and rotational track surface of the driven gear intersect at a predetermined angle. As a result, an inertial body supporting surface serving as a sensor reference plane can be accurately maintained horizontally even at an arbitrary seatback recline angle, and thus the accuracy of the acceleration sensor can be improved.

A seat belt retracting and locking apparatus and an automotive seat including a seat belt retractor, a sensor having a sensing seat and a sensing ball, and a locking mechanism. When the locking mechanism is in a locking state, the sensing seat is fixed in an initial position. When the locking mechanism is in an unlocking state, the sensing seat is rotatable. When the seat belt retracting and locking apparatus and the automotive seat are in a normal state, the sensing seat is locked in the initial position by the locking mechanism, and the angle and the position of the sensing seat are not affected by a change in the speed of a vehicle, so that relative positions between the sensing ball, a pawl, and a ratchet do not change, thereby improving the stability of the performance of the apparatus and seat.