PURPOSE: To increase not only the image resolution but the quality of picture, by using a light emitting diode array in which the light emitting diodes are arrayed in plural rows and alternately and complementarily with every adjacent picture elements for a light source of exposure.

CONSTITUTION: When a light emitting diode 10 is driven, the record picture signals 12 are divided into the picture signals of odd- and even-number picture element rows through a dividing circuit 13. In the case of an exposure of the odd-number picture element row, the off-number picture element row signals sent from the circuit 13 are made to pass through a shift register 14 and then transferred to a latch memory 16 when the odd-number picture element row in a line of the signals 12 is arranged perfectly. Thus a light emitting diode array 20 of the 1st row is actuated by driving a driver 18 for a time corresponding to the transmitting time of signals equivalent to a line. Furthermore the contents of the memory 16 is replaced with the next odd-number picture element row when the said element row is arranged in the register 14. Then the array 20 is actuated again by the driver 18. An exposure of the whole odd-number picture element row is carried out on a photoreceptor that is traveling in a speed V. The same procedure is also given to the even-number picture element row.