To provide a laser plate making apparatus having a small size and a simple circuit configuration by preventing generation of moire.

The laser plate making apparatus comprises supply means 6, 7, 8, 9 for supplying image data signals (a), generating means 3, 4 for generating noise waveform signals (n), and modulating means 2 for pulse-width modulating the signals (a) from the means 6, 7, 8, 9 according to the signals (n) from the means 3, 4. A laser diode 10 is driven by a PWM signal for generating pulses at random obtained according to the pulse-width modulation to make a printing plate.