A focusing adjustment apparatus includes a focusing unit, a first acquisition unit, a second acquisition unit, and a control unit. The focusing unit outputs a first signal for a focusing operation. The first acquisition unit acquires first information, which is related to characteristics of a signal used for outputting the first signal, and second information, which is related to characteristics of a captured image and is predetermined. The second acquisition unit acquires third information on aberrations of an imaging optical system. The control unit calculates a correction value based on the first information, the second information, and the third information. By using the correction value, the control unit changes the first signal, output from the focusing unit, to a second signal used in the focusing operation.