An optical line sensor 1 includes an illumination unit 2, a light receiving unit 3, and a pair of holding members 4 separably attached to the light receiving unit 3 at both ends in a main scanning direction. The illumination unit 2 includes fitting portions (protrusions 25) at both ends in the main scanning direction. Each of the holding members 4 includes a fitted portion (hole 41). In a state where the fitting portion and the fitted portion are fitted, the illumination unit 2 is positioned so that the irradiation optical axis of light emitted from the illumination unit 2 overlaps the light receiving optical axis at a position substantially coinciding with a reading line of the light receiving unit 3 and is integrally held with the light receiving unit 3.

An optical line sensor 1 includes an illumination unit 2, a light receiving unit 3, and a pair of holding members 4 separably attached to the light receiving unit 3 at both ends in a main scanning direction. The illumination unit 2 includes fitting portions (protrusions 25) at both ends in the main scanning direction. Each of the holding members 4 includes a fitted portion (hole 41). In a state where the fitting portion and the fitted portion are fitted, the illumination unit 2 is positioned so that the irradiation optical axis of light emitted from the illumination unit 2 overlaps the light receiving optical axis at a position substantially coinciding with a reading line of the light receiving unit 3 and is integrally held with the light receiving unit 3.

An image reading device includes an image reading chip that reads an image, and an optical unit that forms a reduced image of the image on the image reading chip. The image reading chip includes: a first pixel and a second pixel that performs photoelectric conversion, and generates a first pixel signal and a second pixel signal, respectively; a first readout circuit and a second read out circuit that is electrically connected to the first pixel and the second pixel, respectively, and outputs a first readout signal and a second readout signal, respectively; and a control circuit that controls operations of the first readout circuit and the second readout circuit. The first pixel and the second pixel are provided side by side along a long side of the image reading chip. The first readout circuit, the second readout circuit, and the control circuit are provided along the long side.

Provided is a scanner having sixteen or fewer sensor chips capable of scanning an A4 document; an optical unit that reduces and focuses an image of an A4 document on the sensor chips; and a generator that synthesizes images of the A4 document read by the sensor chips, and generates image data.