A focus state detection apparatus has a sensor that senses light rays that pass through a lens subjected to focus detection and is composed of a plurality of photoelectric converter elements, a charge accumulation unit that accumulates pixel signals obtained by the sensor, a first accumulation controller, a second accumulation controller, a first storage unit that stores each accumulated signal of each of the plurality of areas accumulation-controlled by the first accumulation controller, a second storage unit that stores the accumulated signal of the combined area accumulation-controlled by the second accumulation controller, and a defocus state detector that detects a defocus state of the area from the accumulated signal stored in either the first storage unit or the second storage unit.