A control/data flow analysis unit analyzes the control flow and the data flow of a sequential processing program, and a fork point candidate determination unit determines fork point candidates taking this as the reference. A best fork point candidate combination determination unit determines the best fork point candidate combination by taking as the reference the result from the evaluation of the parallel execution performance of a test fork point candidate combination by a parallel execution performance evaluation unit, and a parallelized program output unit generates and outputs a parallelized program by inserting a fork command based on the best fork point candidate combination.