To convert a ladder program into a C language program, easily generate a program operating on a CPU substrate even without the knowledge for the C language program, and make effective use of an existing program asset.

The program conversion processing apparatus includes: storage means 20 which stores a program conversion table 50 recording a C language command corresponding to a ladder command; and information processing means 10 which converts the input ladder program command into the C language command using the program conversion table 50 to generate a C language program from the ladder program. The conversion result is sequentially stored in a conversion data storage area 70 in the storage means 20.