In an overturn determination process, it is determined that a race kart that is a player object is to be overturned if the race kart is changed into a predetermined pose. In an overturn process, the race kart is forcedly overturned and spun only during a first predetermined time period T1 by experiencing external forces that causes an overturn, and the race kart is rotated by inertia only during a second predetermined time period T2 without experiencing the external forces. Then, a process is performed for bringing the direction of the player kart's height close to the normal vector of the ground and bringing the traveling direction of the race kart close to the pre-overturn traveling direction, whereby the race kart is recovered to a state capable of running again. While the race kart is overturned, an operation control process is not performed, and an operation input from the controller is not accepted.