To provide the subject method constituted so as to be capable of manufacturing a tire good in appearance by preventing the so-called light trouble of the tire generated at the time of the vulcanization of the tire by detecting whether the air leak amount of a mold for vulcanizing and molding the tire is proper or by correcting the air leak amount.

One ends of the exhaust holes formed at the cast joint parts X of piece blocks 3a, 3b are closed and an air supply means not shown in Fig. is connected to the other end parts thereof and the piece blocks 3a, 3b thus constituted are immersed in a water tank and air is supplied under pressure (e.g.; 0.01-0.1 MPA) from the air supply means to detect the air leak region (the position of air bubbles blown into the water tank) and air leak amount (the bubble blow-out amount in the water tank) of the piece blocks 3a, 3b to perform the detection of the air leak amount.