Abstract: A scanning exposure apparatus includes a first movable stage being movable while carrying a first object thereon, a second movable stage being movable while carrying a second object thereon, a projection optical system for projecting a pattern, a control system serviceable to scan the first and second movable stages in a timed relation and relative to the projection optical system and to project a pattern of the first object onto the second object through the projection optical system, a first reference plate fixedly mounted on the first movable stage, a second reference plate fixedly mounted on the second movable stage, and a detecting system serviceable to scan at least one of the first and second movable stages to detect a relative positional relationship between alignment marks of the first and second reference plates to thereby determine a scan direction of one of the first and second movable stages.