PURPOSE: To enable correction due to patch even when the correcting area of a compiled code object is smaller than the sizes of a patch image and a branching instruction.

CONSTITUTION: When translating a source program, label information showing the list of the branch destinations of branching instructions contained in a mechanical word instruction sequence inside the compiled code object is outputted to a file 11 by a compiler 2. A decision part 61 inputs correction information 13 and a patch image 14 and when the size of the correcting area is smaller than the sizes of the patch image and the branching instruction, a destruction correcting means 64 is started. The area, which is not defined as the branch destination by the label information, just before or just after the correcting area is decided as a destroying area by the means 64, an instruction for branching to a patch area is inserted to an area composed of the correcting area and the destroying area, and a mechanical word instruction existent in the patch image and the destroying area and an instruction for branching just after the area are stored in the branch destination of the patch area.