1. An image sensor having a pixel array with a plurality of pixels arranged in rows and columns, the image sensor comprising: a plurality of light-receiving units which are respectively formed in the pixels in the pixel array; a signal processing unit configured to read pixel signals generated by the light-receiving units to perform a signal process; and a timing control unit configured to control a switching timing of the signal processing unit such that pixels of a same color in a same column of different rows in the pixel array are simultaneously selected and subjected to the signal process.