Abstract: A production plan optimization apparatus includes a traveling salesman problem formulation unit for formulating a problem regarding determining a sequence in which a plurality of workpieces are processed as a traveling salesman problem that satisfies a delivery date constraint based on a delivery date specified for at least one of the plurality of workpieces and a sequence constraint specified for at least one of combinations of the plurality of workpieces and also minimizes a sum of changeover times associated with switching of the workpieces and a processing sequence determination unit for calculating a solution to the traveling salesman problem, by using an annealing processing unit for searching for an optimal solution to a combinatorial optimization problem by simulated annealing or quantum annealing, and determining the sequence in which the plurality of workpieces are processed based on a result of the calculation.