A method for reading out signal charges in a solid-state image pickup unit providing either an improved resolution for a constant vertical integration density or a reduced vertical integration density while maintaining the same resolution. The photoelectric conversion elements of the unit are arranged in a matrix of rows and columns with m rows of photoelectric conversion elements being assigned to each scanning line. Signal charges generated in the photoelectric conversion elements during exposure are transferred to a vertical transfer section in the order of the m-th row to the first row in each scanning line, and then the charges are transferred to a horizontal charge transfer section using a four-phase driving method.