PURPOSE: To decrease the connecting wirings of light emitting diodes and to produce a large-scale dot matrix by applying the output signals complying with pulse width modulation to constant current circuits and executing gradation control.

CONSTITUTION: The image data B1 which is synchronized with a clock signal 12 and is latched in a latch signal 13 applies the color signals 14 which are 3-bit digital signals to the terminals from Q0 to Q2 of a shift register 10 and these signals are inputted to the address terminals from A3 to A5 of a ROM 17. the signals 14 assign the respec tive colors of 23=8 pieces. The ROM 17 outputs 4-bit output signals 18 to the output terminals from d0 to d3 according to the pulse width modulation of 1/8 duty by the program previously stored in correspondence to the input of the signals 14 and the counter signal 16. These signals are inputted respectively to the constant current circuits 7, 8, 9, 9. Driving currents flow selectively to the 1st, 2nd, 3rd light emitting diodes 1, 2, 3, 3 in correspondence thereto and prescribed display colors are displayed. The output signals are applied to the prescribed constant current circuits according to the pulse width modulation by the ROM in accordance with the prescribed color signals in such a manner and, therefore, the wiring of one piece per light emitting diode is possible.