A detection apparatus configured to detect a focus state based on an output signal from an image pickup element capable of outputting an image pickup signal and a phase-difference detection signal includes, a first calculation unit configured to calculate information related to a first phase difference based on the phase-difference detection signal output from the image pickup element, a second calculation unit configured to calculate information related to a second phase difference based on the image pickup signal output from the image pickup element, and a detection unit configured to detect the focus state based on the information related to the first phase difference and the second phase difference.