Focus detection apparatuses, control methods, and storage mediums for use therewith are provided herein. In a focus detection apparatus, a difference amplification unit performs processing for amplifying a difference between an A-image signal and a B-image signal and a CPU determines whether or not a focus state is a false in-focus state on a basis of a result of a correlation calculation performed by a correlation calculation unit on the A-image signal and the B-image signal. The A-image signal and the B-image signal are output from an imaging sensor that receives a pair of luminous fluxes passing through different pupil areas of an imaging optical system.