A generation means 11 generates a uniform random number between 0 and a first probability, which is a probability of a stochastic variable becoming a value within a predetermined interval in a positive range in the first discrete distribution. When a uniform random number less than or equal to a second probability is generated, the second probability being a probability of the stochastic variable becoming a value within a predetermined interval in a second discrete distribution, which is a discrete Gaussian distribution on a one-dimensional lattice the center of which is the origin, the selection means 12 selects, as a random number generation method, an accumulation method in which a functional value defining the second discrete distribution is used. When a uniform random number greater than the second probability is generated, the selection means 12 selects a rejection sampling method as the random number generation method.