A wafer is bonded to a support plate by cutting off, with a cutting blade, an annular portion of the bonded wafer which extends from the outer peripheral edge of the bonded wafer to a position that is spaced radially inwardly toward the center of the bonded wafer by a predetermined distance. Bonding is done by a method that includes a captured image forming step of irradiating the outer peripheral edge of the bonded wafer with light emitted from an irradiating unit and passing through a through hole, and imaging the outer peripheral edge of the bonded wafer with an imaging camera disposed in facing relation to the irradiating unit with the bonded wafer interposed therebetween, thereby to capture an image, and an outer peripheral edge position detecting step of detecting an outer peripheral edge position of the bonded wafer on the basis of the captured image.