A stage apparatus includes a stationary support plate; a Y-direction movable member supported on, and parallel to, the stationary support plate so as to be relatively movable in a Y-direction, the Y-direction movable member including a Y-direction rod portion and a pair of X-direction rod portions, wherein the Y-direction rod portion extends in the Y-direction, and the pair of X-direction rod portions are joined to the Y-direction rod portion to extend in an X-direction both parallel to the stationary support plate and perpendicular to the Y-direction; and an X-direction movable member supported by the pair of X-direction rod portions to be movable in the X-direction relative to the Y-direction movable member. At least one of the pair of X-direction rod portions is rotatable about an axis of the Y-direction rod portion relative to the Y-direction rod portion.