1. A program translator comprising: instruction exchanging means for exchanging one of instructions included in a program for another instruction, the latter instruction specifying an operation equivalent to that specified by the former instruction, the latter instruction designating, as a target of the operation, an execution unit that is different from an execution unit designated as a target by the former instruction; and instruction parallelizing means for placing the instructions in the program, in which the former instruction has been exchanged for the latter instruction by the exchanging means, at such locations as being parallelly executable by a processor.