Provided is a computer device which changes a demonstration image to be displayed when a game is played next, according to a state of proceeding of a main part of the game, and can attract the user's interest on the demonstration image. The computer device comprises a game proceeding control section (game proceeding control module) which causes a game to proceed in response to a user's manipulation; a game proceeding management section (game proceeding management module) which manages a state of proceeding of the game; and a demonstration image generating/outputting section (demonstration image generating/outputting module) which outputs a demonstration image to a monitor before the game is played; wherein the demonstration image generating/outputting section is configured to change the demonstration image to be output to the monitor before the game is played, according to the state of proceeding of the game.