A program parallelizing apparatus, a program parallelizing method and a program parallelizing program capable of creating a parallelized program of better parallel execution performance at a high speed. A fork point determination section extracts all fork points in a sequential processing program, and removes fork points with a static boost value satisfying a static rounding condition. A fork point combination determination section obtains a dynamic boost value and an exclusive fork set for each fork point that appears when the sequential processing program is executed with input data, and removes fork points with a dynamic boost value satisfying a dynamic rounding condition. As a maximum weight independent set problem, the fork point combination determination section obtains an initial combination of fork points, which are not in an exclusive relationship, with the maximum sum of dynamic boost values, and retrieves an optimal combination based on an iterative improvement method. According to the optimal fork point combination, a parallelized program output section creates a parallelized program for a multithreading parallel processor from the sequential processing program.