The present invention enables one to execute scalar replacement in program optimization, more effectively without executing analysis in a method. The present invention is provided with a code conversion unit 110 for generating a machine language code based on a source code of an execution program to be processed, an optimized range determination unit 120 for, for a method in the execution program of the machine language code, finding a range in which an object created in the method does not escape, and a scalar replacement execution unit 130 for executing the scalar replacement in the range in which the object does not escape.