PURPOSE: To partially correct a machine word program in assembler descriptive form with the less amount of computer processing, by providing a means of gathering necessary data automatically from the assembling list of an original program, a combining and editing list, and the machine word program.

CONSTITUTION: An assembler source generation part 13 extracts interface information, required for label processing and address calculation, from the assembling list 17 of an original program and a combining and editing list 18 to relate partially corrected data 2 in the whole of the program, thus generating the assembler source 19 of the original program. Then, a corrected data merging part 14 merges the corrected data 20 in assembler descriptive form into the source 19 to generate a corrected assembler source 21. An assembler processing part 15 assembles the source 21 to generate the partially corrected data 22 of a machine word program.