A semiconductor device comprises a plurality of units, each including a sensor unit which accumulates charges upon photoelectric conversion and a storage unit which stores information, and a control unit which controls each of the plurality of units, wherein the control unit sequentially performs, for each of the plurality of units, first operation of comparing a reference voltage with an output signal from the sensor unit based on the amount of accumulated charges and second operation of storing information based on the comparison result in the storage unit corresponding to the sensor unit if an output signal from the sensor unit reaches the reference voltage in the first operation, and the control unit is configured to be able to start the first operation for a next unit upon skipping the second operation and skips the second operation in a predetermined period.