Each spoke portion (50) includes a center valley portion (51), and spoke projecting threads (52) formed on both sides of the center valley portion (51). Each of the spoke projecting threads (52) includes an inclined surface portion (54), which protrudes outward in a spoke widthwise direction from a top (53) and inclines downward to a wheel axially back side. The inclined surface portion (54) is formed so that a length thereof in a range of from the top (53) to an outer end of the inclined surface portion (54) in the spoke widthwise direction becomes larger toward a spoke distal end side, and that an average downward inclination angle thereof becomes smaller toward the spoke distal end side. With this configuration, it is possible to increase rigidity of the spoke portion with good balance while avoiding interference with a braking device.