A riding game machine (1) for playing the game of a jet ski race, for example, has a display unit (10) for displaying a simulated image of an object on a wavy surface, and a riding device (20) swingable depending on the simulated image displayed by the display unit (10). The riding device (20) has a riding unit (21) for a player to ride thereon, a handle (22) coupled to the riding unit (21) for changing a direction of travel of the object of the simulated image displayed by the display unit (10), an accelerator lever (23) mounted on the handle (22) for changing a speed of the object of the simulated image displayed by the display unit (10), a pitching member for swinging the riding unit (21) about a horizontal transverse axis, a rolling member for swinging the riding unit (21) about a horizontal longitudinal axis, and a pitching mechanism (24) for actuating the pitching member in relation to travel of the object on the wavy surface in the simulated image displayed by the display unit (10).