The image sensor of the linear type includes a plurality of photoelectric conversion elements, switching elements each having an input terminal connected to each photoelectric conversion element and an output terminal for reading out a detection signal produced from the corresponding photoelectric conversion element, and a scanning circuit for sequentially driving the switching elements. A first common line is connected to output terminals of odd-numbered switching elements. A second common line is connected to output terminals of even-numbered switching elements. A first reading gate has an output terminal and an input terminal connected to the first common line. A first reset gate has an output terminal and an input terminal connected to the first common line. A second reading gate has an output terminal and an input terminal connected to the second common line. A second reset gate has an output terminal and an input terminal connected to the second common line. A third common connecting line is connected between the output terminals of first and second reading gates and a signal output terminal for outputting the detection signals. A reset power source terminal is connected to the output terminals of the first and second reset gates. A control circuit operates with the sequential driving of the switching elements for controlling the first and second reading gates and the first and second reset gates so as to output the detection signals while sequentially resetting the photoelectric conversion elements.