An imaging device includes a pixel unit having a plurality of pixels forming a plurality of rows and a plurality of columns, and a readout unit that divides the pixel unit into a plurality of pixel blocks based on a division pattern, each pixel block including at least two pixels, and combines signals from the at least two pixels included in one pixel block to generate one signal for each of the pixel blocks. A detection unit detects a change in signal values between a plurality of signals sequentially generated by the readout unit of the one pixel block. A control unit controls the readout unit to output a signal individually from each of the pixels included in at least one pixel block in response to detecting a change in the signal values, and controls the readout unit so that the division patterns are different in at least two frames.