To provide an illegal action inspection method for a game machine in which if illegal action such as replacement of an electronic part such as a ROM exists or not can be easily inspected by actuating variation pattern display means in plural game machines of the same machine type, and checking stopped patterns after variation action of the variation pattern display means.

In starting plural game machines of the same machine type each provided with a variation pattern display means 29 to start variation action when a pattern starting signal is inputted, and stop it at patterns in accordance with timing of the pattern starting signal at a specified time after that, and a profit condition generating means 37 to generate a profit condition when the stopped patterns in the variation pattern display means 29 become specified patterns preset, an inspection starting signal as a substitute to the pattern starting signal is inputted at the same timing simultaneously to the respective game machines to vary patterns in the variation pattern display means 29 in the respective game machines, and stopped patterns in respective variation pattern display means 29 after variation action are compared with each other, thereby if illegal action exists or not is inspected.