A pair of toothed wheels that mesh with each other includes a plateau portion. The surface of the plateau portion is a plateau-structure surface formed on each tooth face of each of the pair of the toothed wheels, with peak portions of convexities, out of a plurality of concavities and the convexities provided on the each tooth face, being flat. A reduced valley depth Rvk of the plateau portion of one of the pair of the toothed wheels as defined in JISB0671-2 is greater than the reduced valley depth Rvk of the plateau portion of the other of the pair of the toothed wheels. The area occupied by the concavities in the plateau portion of the one of the toothed wheels is larger than the area occupied by the concavities in the plateau portion of the other toothed wheel.