In a light spot position detection device, in one frame of operation, under control of a control unit, pixel data obtained in a pixel section in exposure of a solid-state image sensor in synchronization with light emission of a light emitting element are added to corresponding storage portions in a memory unit, and pixel data obtained in exposure of the image sensor asynchronous to the light emission of the light emitting element are subtracted from the corresponding storage portions, to store pixel data of only signal light in the storage portions. A given number of frames of operation are repetitively performed to accumulate pixel data of only the signal light in the storage portions. The position of a light spot on the pixel section is calculated based on the pixel data of only the signal light and outputted whether the storage portions are saturated or not with the pixel data.