To reuse a broken bat through repair of the bat, by performing a reinforcement by winding a filament or cloth impregnated with a resin on to the surface of the bat to be hardened, and improve durability of a new bat to make the bat have a long life.

When a wooden bat for baseball which is broken into a tip part and a rear end part is repaired, the broken parts are adhered by applying an adhesive to a broken surfaces 3. Next, a reinforcement is performed by winding a filament 6 impregnated with a resin over a prescribed range of a surface including the broken parts. The filament 6 to be used is made of glass fiber, the filament 6 that monofilament of 4 to 20d is bundled into multifilament in a 10 to 500 strands state is suitable and is impregnated with an unsaturated polyester resin. At the time of the reinforcement, the reinforcement by FRP molding may be performed by using a cloth of nonwoven fabric made of glass filament and impregnated with an unsaturated polyester resin.