1. An image processing apparatus comprising: a focusing position specification unit configured to specify a first focusing position for a first frame of a plurality of frames forming a time-lapse moving image; a parallax image acquisition unit configured to acquire a first parallax image and a second parallax image, which are contained in a first image file corresponding to the first frame, from a recording medium; a shift amount calculation unit configured to calculate a first shift amount for a first focusing position shift to be performed on the first parallax image and the second parallax image for focusing on the first focusing position; a refocused image generation unit configured to perform the first focusing position shift with the first shift amount on the first parallax image and the second parallax image, and to combine the first parallax image and the second parallax image after the first focusing position shift to generate a first refocused image; and a time-lapse moving image generation unit configured to replace the first frame by the first refocused image to regenerate the time-lapse moving image.