Two workpieces composed of a resin workpiece and a resin workpiece, or composed of a resin workpiece and a glass substrate are bonded to each other such that troubles, such as an alignment shift and breakage etc. are not generated, while ensuring bonding uniformity. A first workpiece is placed on an inverting stage of an inverting stage unit, a second workpiece is placed on a work stage of a pressurizing stage unit, and UV light is radiated from a light irradiation unit. Then, the inverting stage is inverted 180°, the workpieces are overlapped each other on the work stage, and the workpieces are pressurized and pre-bonded to each other. Then, the workpieces in the pre-bonded state are transferred to a heating stage by a transfer means, the temperature of the workpieces is increased to a predetermined temperature by heating the workpieces, and the temperature is maintained until bonding is completed.