A pneumatic tire is molded by using a vulcanizing mold in which blades 20, each composed of a metal thin plate having an inclined portion 20a in the depth direction and a plurality of through holes 20G with the same sectional form as that of projections to be formed in the sipe in the inclined portion 20a are buried in a groove portion corresponding to the tire block of the vulcanizing mold, thereby forming 3D sipes having unevenness in the radial direction of the block and a plurality of pairs of projections in the inclined portion in the block of the tire. Thereby, when longitudinal force is applied to the tire, adjacent small blocks of the block come into close contact with each other only at the positions of the projections of the 3D sipes, thereby making it possible to ensure the block stiffness of the pneumatic tire 10 without reducing the drainage function.