To efficiently dissipate heat generated on an object to be cooled.
In a base fin 121, a first slit 1,220 is formed that extends in a radially outward direction along a heat dissipation fin 12 in a radially outer peripheral side of the heat dissipation fin 12. The base fin 121 is branched into a front side first branch fin 1,221 that is formed on the front side in the curvature direction and a back side first branch fin 1,222 that is formed on the back side in the curvature direction. In the back side first branch fin 1,222, a second slit 1,230 is formed that extends in a radial outward direction along the heat dissipation fin 12. The back side first branch fin 1,222 is formed with a front side second branch fin 1,231 on the front side in the curvature direction and a back side second branch fin 1,232 on the back side in the curvature direction. At this time, a second slit's inner peripheral end 1,233 that is formed by the second slit 1,230 is located in more outward in the radial direction than a first slit's inner peripheral end 1,223 that is formed by the first slit 1,220.
YAMASHITA TAKAMASA
INOUE YOSHINORI
