In a case where a thinning operation is implemented at the point when signal charges are read out from each of pixels to thin out pixel information by lines (row), the thinning may be performed only in the vertical direction, but not in the horizontal direction. In an all-pixel-read-out type CCD image pickup element, a discharge controlling section is provided in each of VH transfer stage sections transferring signal charges from vertical CCDs to a horizontal CCD, and where a thinning mode is selected, among those signal charges transferred from a plurality of the vertical CCDs, those of a given set of columns are stopped and discharged at the respective discharge controlling sections, and those of the rest of columns are transferred to the horizontal CCD, and at the same time, those of a given set of lines (rows) are stopped and discharged for all columns, thereby performing the thinning operation over the pixel information in both the vertical and horizontal directions at the VH transfer stage.