A dependent element group which is invertibly contractible is found by using program analysis information including a plurality of dependent elements representing dependent relationships of statement and control, the statement and the control being included in a program. Next, a program dependence graph in which dependent elements are made to be contracted is generated by contracting the found dependent element group. The number of vertices and the number of edges of the program dependence graph are reduced by the contraction of the dependent elements, so that a program dependence graph with a rough granularity can be generated. As a result, a calculation amount (calculation time) necessary for optimization processing such as parallel processing of the program can be reduced. That is, by generating the contracted program dependence graph having invertibility, it is possible to realize the analysis and optimization of large-scale software in a realistic time.