The apparatus of the present invention includes a block diagram dividing unit that divides a block diagram into a plurality of pieces at a branch point, connects a branch point block element to one end of a data line which has been connected to the branch point at each divided piece and thereby generates a plurality of block diagram pieces, a program instruction generator that generates program instructions for performing processing on each block diagram piece, an execution sequence determining unit that determines an execution sequence of generated program instructions, a structural information generator that generates structural information of each of the block diagram pieces and a program generator that arranges the program instructions according to the execution sequence, writes structural information of each block diagram piece into a comment line of each of the program instructions corresponding to each of the block diagram pieces and thereby generates a program.