To prevent a fraud by sharpshooting of a random number by generating the random number using a pulse width modulation (PWM).

The pulses with different duty ratios are periodically sampled by the number of bits and defined as the random number. The ON/OFF periods (time width) are changed by defining one time of being a high voltage as "High" and a time of being a low voltage as "Low" using the PWM. This constitution makes it difficult for a player to perform the sharpshooting of a big winning period so as to prevent the fraud by the sharpshooting of the random number.