In an exposure apparatus, an exposure stage is moved from an exposure position to a work piece feeding and discharging position, exposure light is emitted from a light emitting unit to a first alignment mark on a first mask and an image of the first alignment mark is projected on a first reflecting material, and a reflected image of the first alignment mark image is detected by the alignment microscope thereby detecting position of the first mask, and when the exposure stage is moved to a reversal handing over position, exposure light is emitted to a second alignment mark of a second mask from the light emitting unit, an image of a second alignment mark of a second mark is projected on a second reflecting material, and a reflected image of the projected second alignment mark image is detected by the alignment microscope thereby detecting position of the second mask.