An image sensor has image sensor ICs mounted linearly thereon. Each of the image sensor ICs comprises a light receiving device circuit array having light receiving devices, a reset circuit device array, and a plurality of switches. The light receiving devices have output terminals that output output signals in accordance with an amount of light received. The reset circuit device array initializes the output terminals of the light receiving devices in an initialization mode. The switches drive the reset circuit device array and are configured to be maintained in a conductive state during an accumulation period so that an initialization potential is outputted by the output terminal of each of the light receiving devices of one of only a first one of the linear image sensor ICs, only a last one of the linear image sensor ICs, and all of the linear image sensor ICs.