An optimization device includes: search circuits, each configured to: hold values of state variables included in an evaluation function representing an energy value; calculate a change value of the energy value for each of state transitions which occurs in response to a change in one of the state variables; and determine stochastically whether to accept one of the state transitions according to a relative relationship between the change value of the energy value and thermal excitation energy, based on a set temperature value, the change value, and a random number value; and a controller configured to: acquire statistical information regarding a transition of a temperature value in each search circuit; determine a temperature value to be set in each search circuit based on the statistical information; set the temperature value for each search circuit; and exchange the temperature value or the values of the state variables between the search circuits.