When stochastically deciding, based on a change in energy and a random number relating to thermal excitation, whether to accept any of a plurality of state transitions according to the relative relationship between the change in energy and thermal excitation energy, a transition control unit adds an offset to the change in energy, performs control so that the offset at a local minimum where energy is locally minimized is larger than an offset when the energy is not minimized, holds transition information (a transition number) indicating a previous state transition, and prohibits, based on a decoding result for the held transition information, a first state transition out of the present state transition candidates.