An image sensor has a plurality of unit pixels each provided with a plurality of photoelectric conversion portions and a floating diffusion portion, and an analog-digital converter. The analog-digital converter is controlled to: convert a reset level of the floating diffusion portion by counting in a first or second direction to acquire a first noise signal, acquire a first optical signal by counting in the first direction an analog signal of a first photo charge accumulated in a first photoelectric conversion portion, acquire a second noise signal by counting in the second direction a potential that the floating diffusion portion has after the first optical signal is acquired, and acquire a second optical signal by counting in the first direction an analog signal of a second photo charge accumulated in a second photoelectric conversion portion.