An A/D conversion section (11) counts clocks whose frequency corresponds to the size of output signals from pixels (10a), and digitalizes the result so as to create count values, and also calculates a difference between a first count value that relates to the output signal during a reset period of a pixel, and a second count value that relates to the output signal during an exposure period of the pixel, and then outputs this difference as an imaging signal for this pixel. A control unit (12) controls the A/D conversion section such that the length of the counting period of the first count value is equal to the length of the counting period of the second count value.