Motivation is provided for a game character in accordance with the situation or the progress of a game, and is reflected in the character's operation. In a game machine, a character displayed on a monitor screen performs various game-related operations in response to an instruction provided from a controller. The game machine includes a situation determining portion for determining whether a predetermined game-related situation has occurred. A motivation-level setting portion sets the motivation level, influencing the character's operation, in response to an occurrence of the situation. An operation control portion controls the character to operate in response to the set motivation level. In this manner, the motivation level is provided for the character in accordance with an occurrence of the situation, and the character is operated with the characteristics and the ability corresponding to the provided motivation level.