There is provided an image processing apparatus comprising: a sensor including a plurality of pixels each including a light receiving element, and a scanning circuit for reading out signals in time sequence from the plurality of pixels; and a drive circuit which supplies pulses for driving the scanning circuit, wherein the drive circuit is so arranged to output at least a first pulse and a second pulse smaller than the first pulse, the drive circuit supplying the first pulse to the scanning circuit when a first resolution is selected, and supplying the first pulse and the second pulse to the scanning circuit when a second resolution lower than the first resolution is selected.