A vulcanization mold in which an annular mold for forming a tire tread of a pneumatic tire is split in a circumferential direction into a plurality of sector molds and the sector molds are moved in directions toward the center and combined with each other to clamp a raw tire on the inner side to vulcanization mold the raw tire, each of the sector molds having blades (6, 7, 8, 9, 10, 11, 12, 13) implanted on a mold surface thereof, the blades being thin plate-like members extending in a tire widthwise direction and being used to form groove lines on the tire tread, each of the blades having a blade proximal end portion (6a, 7a, 8a, 9a, 10a, 11a, 12a, 13a) to be embedded into the sector mold, a blade distal end side thick portion (6c, 7c, 8c, 9c, 10c, 11c, 12c, 13c) expanded in a thicknesswise direction on the distal end side, and a blade connection portion (6b, 7b, 8b, 9b, 10b, 11b, 12b, 13b) that connects the blade proximal end portion and the blade distal end side thick portion to each other, wherein a blade density (Dc, De) that is a number of the blades implanted on the sector mold per unit length in a circumferential direction is lower at the blades in circumferential end portion side regions than at the blades in a circumferential central portion side region of the sector mold, and wherein a multiplication value obtained by multiplying the blade density by a sweep area (Sc, Se) that is a difference where a cross sectional area of the blade connection portion is subtracted from an area from the blade distal end side thick portion to the mold surface with a width equal to a maximum width of a thickness (Wc, We) of the blade distal end side thick portion in a cross sectional shape perpendicular to the tire widthwise direction of the blade is smaller at the blades in the circumferential end portion side regions than at the blades in the circumferential central portion side region of the sector mold. each of the sector molds having blades (6, 7, 8, 9, 10, 11, 12, 13) implanted on a mold surface thereof, the blades being thin plate-like members extending in a tire widthwise direction and being used to form groove lines on the tire tread, each of the blades having a blade proximal end portion (6a, 7a, 8a, 9a, 10a, 11a, 12a, 13a) to be embedded into the sector mold, a blade distal end side thick portion (6c, 7c, 8c, 9c, 10c, 11c, 12c, 13c) expanded in a thicknesswise direction on the distal end side, and a blade connection portion (6b, 7b, 8b, 9b, 10b, 11b, 12b, 13b) that connects the blade proximal end portion and the blade distal end side thick portion to each other, wherein a blade density (Dc, De) that is a number of the blades implanted on the sector mold per unit length in a circumferential direction is lower at the blades in circumferential end portion side regions than at the blades in a circumferential central portion side region of the sector mold, and wherein a multiplication value obtained by multiplying the blade density by a sweep area (Sc, Se) that is a difference where a cross sectional area of the blade connection portion is subtracted from an area from the blade distal end side thick portion to the mold surface with a width equal to a maximum width of a thickness (Wc, We) of the blade distal end side thick portion in a cross sectional shape perpendicular to the tire widthwise direction of the blade is smaller at the blades in the circumferential end portion side regions than at the blades in the circumferential central portion side region of the sector mold.