A computer generates a parallel program, based on an analysis of a single program that includes a plurality of tasks written for a single-core microcomputer, by parallelizing parallelizable tasks for a multi-core processor having multiple cores. The computer includes a macro task (MT) group extractor that analyzes, or finds, a commonly-accessed resource commonly accessed by the plurality of tasks, and extracts a plurality of MTs showing access to such commonly-accessed resource. Then, the computer uses an allocation restriction determiner to allocate the extracted plural MTs to the same core in the multi-core processor. By devising a parallelization method described above, an overhead in an execution time of the parallel program by the multi-core processor is reduced, and an in-vehicle device is enabled to execute each of the MTs in the program optimally.