PURPOSE: To provide the random number generator generating a logic '1' in the incident probability of m/2n.

CONSTITUTION: Basic random number generating circuits 11a-11c generate '1' with a probability of 1/2. Each output of the basic random number generating circuits 11a-11c is given to each of random number decision circuits 12a-12c connected longitudinally. Each output of the random number decision circuits 12a-12c is given to each of random number adder circuits 13a-13c connected longitudinally. Each of probability setting circuits 14a-14c gives '0' or '1' to each of the random number adder circuits 13a-13c. When '1' is generated in one basic random number generating circuit, since outputs of the random number decision circuits at the post stage in the longitudinal direction are all zero, an output P is '1' with an incident probability of m/2n by the setting from (0, 0, 0) to (1, 1, 1) in the probability setting circuits 14a-14c.