PURPOSE: To automate the updating work of another part program in a range influenced by the correction/change of an existing part program and the updating work of a synthetic source program formed by using the updated part program.

CONSTITUTION: A preparation processing part 20 divides a source program 10 into plural part programs in each function, variable, or the like and registers each part detailed information 42 in a part file 40. Parts mutual relation information 41 expressing parts mutual relation among respective part programs is registered in the file 40. An updating processing part 70 judges an influenced range based upon the information 41 at the time of updating parts and updates the information 42 to be influenced. At the time of updating a synthetic source program, the parts detailed information of updated parts out of parts specified by a synthesis specification file 60 is extracted from the file 40 and substituted for corresponding parts in a synthetic program 50.