A control unit 6 causes a vertical scanning circuit 3 to cyclically select any one-dimensional pixel line from among pixel lines 21 to 23 each time a prescribed H period elapses, and controls a read circuit 5 and a horizontal scanning circuit 4 so as to read out pixel signals of an object which has been exposed by the selected pixel line. The control unit 6 further controls a vertical movement unit 8 in such a manner that the scanning speed S satisfies S=P/4H, where P is the arrangement pitch in the vertical direction of the pixel lines 21 to 23 and H is the H period.