To obtain a satisfactory relief effect by fixing a gap forming implement with a leg by a relief cast so as to form a specified gap between the after-fixation cast sole and the foot sole at the time of winding the relief cast, which protects a broken bone part of the leg from excessive load.

At the time making Gibbs, a bellows bag 2 is arranged with an air vent closed in a hard-resin-made protection case 20, a foot 3 is placed thereon, and a cast 1 is wound and fixed. After the cast 1 is hardened, when the air vent 21 is released, the bellows bag 2 is expansible so as to complete a relief walking cast excellent in a weight bearing effect. At this time, the protection case 20 has a function of protecting the bellows bag 2 from the cast 1, whereby the bellows bag 2 can be expanded and touch in the cast 1. Further, the cast 1 has a gap 4 between the sole of the foot 3 and the cast sole 10, whereby in walking with cast, the bellows bag 2 absorbs load force due to walking load so as to exhibit a satisfactory relief cast effect.