A game apparatus includes a CPU, and the CPU executes a game program stored in a game cartridge. During a game, the CPU corrects an ultraviolet ray value detected by an ultraviolet ray sensor in such a manner as to render equal or approximate to a setting value of the ultraviolet ray value in the game, and uses a corrected ultraviolet ray value for the game. In addition, the CPU detects an accumulated value of the ultraviolet ray to which a player is exposed during the game, and when the accumulated value is equal to or larger than a predetermined amount (dangerous level), prohibits a game process.