A focus adjustment unit of the present invention comprises a phase difference detection section for detecting extreme values, based on the image data, a periodicity-containing subject determination section for determining a periodicity-containing subject in the case where the phase difference detection section detects many extreme values having a high degree of correlation, and a control section for, when a periodicity-containing subject has been determined, determining whether or not a difference between a position of the focus lens shown by an extreme value corresponding to a position that is closest to a current focus lens position, and the current focus lens position, is outside a specified range, and if it is determined that the difference is outside the specified range, carrying out a focus adjustment operation based on the extreme value corresponding to the position that is closest to the current position of the focus lens.