This invention includes accumulation units (102a, 102b) which accumulate signals obtained by sensing units (111a, 111b), an area determination unit (103, 100) which sets the size of an area of a sensing unit to be segmented into a plurality of areas on the basis of the information of a lens to be focus-detected, accumulation control units (104a-104c, 105) which control, for each of the areas, accumulation of signals obtained in a plurality of areas by the accumulation units, and a defocus detection unit (100) which detects defocus states in the respective areas from accumulated signals from a plurality of areas.