A random number generator includes a flip-flop in which an output state (0
or 1) becomes definite according to a phase difference between signals
inputted to two input units, a delay unit for producing the phase
difference in these two input signals, and a feedback circuit for
controlling the phase difference so that an occurrence ratio of 0 or 1 of
an output from the flip-flop by the input signals is constant within a
specified repetition cycle.