When plate-shaped components are inserted in the correct order and orientation into component insertion grooves of a component assembly jig, the component insertion grooves are blocked by the plate-shaped components, and the blowing of compressed air is stopped. When the blowing of compressed air from the component insertion grooves is stopped, the pressure in a compressed-air path increases, and an alignment-complete lamp is illuminated. Using the component assembly jig enables an assembly operation for overlapping the plurality of plate-shaped components in the correct order and orientation, without excess or deficiency, to be efficiently performed without error.