An exposure apparatus has a triangular shaped stage which is movable in a two-dimensional
plane while holding a substrate. The stage has a reflecting surface provided on
a side face of the stage so that the surface extends in a specific direction intersecting
Y axis and X axis. An interferometer radiates a beam onto the reflecting surface
to measure a position of the stage in a direction perpendicular to the specific
direction. Using the measured position and an angle of the specific direction,
a calculator can calculate the position of the stage on rectangular coordinate
system defined by X and Y axes. The size and weight of the stage can be reduced,
and the throughput of the exposure apparatus is improved.
