To obtain reduced image data with satisfactory color balance by enhancing sensitivity.

This method includes a step, where charges of a some of a plurality of photoelectric conversion elements 2 are read to vertical charge transfer lines 3 (3-1 to 3-6), a step where the charges on the vertical charge transfer lines are transferred in the vertical direction, a step where charges of two photoelectric conversion elements or more are summed on the vertical charge transmission lines, by reading charges from other photoelectric conversion elements to the vertical charge transmission lines, a step where charges are transferred from a part of a plurality of the vertical charge transmission lines to a horizontal charge transmission line 6, a step where charges on the horizontal charge transmission line are transferred in the horizontal direction, and a step where charges from the two vertical charge transmission lines or more are summed on the horizontal charge transmission line, by transferring the charges from the other vertical charge transmission lines to the horizontal charge transmission line.