Abstract: A reception unit receives an execution history file of a target program and a software structure file of the target program. An association unit associates each piece of execution element information of the execution history file and each piece of component information of the software structure file with each other, thereby generating an association file. A determination unit determines each execution element and a parent element of each execution element as important elements by referring to the software structure file based on the association file, thereby generating an important element file indicating each important element. A visualization unit generates a visualization diagram indicating the structure of the target program in a state where each important element has been emphasized, based on the important element file and the software structure file.