1. A focus detection apparatus comprising at least one processor or one circuitry which functions as: a focus detection unit that detects a defocus value; a first calculation unit that obtains a correction value for shifting an in-focus position by a first method, the in-focus position being based on the defocus value; a second calculation unit that obtains a correction value for shifting the in-focus position by a second method that is different from the first method, the in-focus position being based on the defocus value; a conversion unit that converts the correction value obtained by the second method to a correction value of the first method by changing units; a storage unit that stores the correction value obtained by the first calculation unit or the correction value converted by the conversion unit; and a control unit that controls driving of a focus lens to a lens position based an a value obtained by correcting the defocus value by the correction value stored in the storage unit, wherein, in the second method, at least one of a plurality of images obtained by driving the focus lens to a plurality of different lens position is selected by a user, and the correction value is calculated based on the defocus value corresponding to the selected image.