A program optimization method for converting program source code written in a programming language into machine language includes steps of: analyzing a target program and detecting an exception generative instruction, which may generate an exception, and exception generation detection instructions, which brunches a process to an exception process when an exception occurrence condition is detected and an exception has occurred. The method also includes steps of dividing the exception generation detection instructions into first instructions, for the detection of exception occurrence conditions, and into second instructions, for branching processes to the exception process when the exception occurrence conditions are detected; and establishing dependencies among program instructions, so that when one of the exception occurrence conditions is detected the process is shifted from a first instruction to a second instruction, and so that when none of the exception occurrence conditions are detected, the process is shifted from a first instruction to an exception generative instruction.