PURPOSE: To obtain an excellent picture reading output by eliminating switching noise and an offset voltage of a switching element for signal read.

CONSTITUTION: The switching noise is prevented from appearing at the read output by providing preamplifiers A1∼An to the pre-stages of the switching elements S11∼Sin to read signals from photoelectric converting elements D1∼Dn. Moreover, picture reading signals are obtained by detecting output signal differences among the preamplifiers A1∼An before and after an input terminal potentials of the preamplifiers are reset.