A golf club shaft formed of fiber-reinforced resin layers, wherein the golf club shaft satisfies Formula 1 below and strength reference values of to below when flex in a cantilever bending test is defined as x [mm], a mass of the golf club shaft is defined as M [g], and a length thereof is defined as L [mm]. M × L / 1168 < 49.66 e − 0.0015 x Three-point bending strength at T-90, which is a position 90 mm apart from a small-diameter end part, is 800 N or more; Three-point bending strength at T-175, which is a position 175 mm apart from the small-diameter end part, is 400 N or more; Three-point bending strength at T-525, which is a position 525 mm apart from the small-diameter end part, is 400 N or more; and Three-point bending strength at B-175, which is a position 175 mm apart from a large-diameter end part, is 400 N or more, wherein the fiber-reinforced resin layers include: a bias layer that is formed by overlapping fiber-reinforced resin layers, in which orientation directions of reinforcing fibers are +35° to +55° and -35° to -55 relative to a longitudinal direction of the shaft, with each other; a straight layer (6, 7, 8) that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is -5° to +5° relative to the longitudinal direction of the shaft; and a hoop layer (3A, 5A) that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is +85° to +95° relative to the longitudinal direction of the shaft, wherein the hoop layer is formed of two fiber-reinforced resin layers of a first hoop layer and a second hoop layer, the two hoop layers (3A, 5A) have an overlapped portion, one end of the overlapped portion is located between 125 mm and 375 mm from the small-diameter end part of the shaft, and the other end of the overlapped portion is located between 675 mm and 925 mm from the small-diameter end part of the shaft. Three-point bending strength at T-90, which is a position 90 mm apart from a small-diameter end part, is 800 N or more; Three-point bending strength at T-175, which is a position 175 mm apart from the small-diameter end part, is 400 N or more; Three-point bending strength at T-525, which is a position 525 mm apart from the small-diameter end part, is 400 N or more; and Three-point bending strength at B-175, which is a position 175 mm apart from a large-diameter end part, is 400 N or more, a bias layer that is formed by overlapping fiber-reinforced resin layers, in which orientation directions of reinforcing fibers are +35° to +55° and -35° to -55 relative to a longitudinal direction of the shaft, with each other; a straight layer (6, 7, 8) that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is -5° to +5° relative to the longitudinal direction of the shaft; and a hoop layer (3A, 5A) that is formed of a fiber-reinforced resin layer in which an orientation direction of the reinforcing fiber is +85° to +95° relative to the longitudinal direction of the shaft, wherein the hoop layer is formed of two fiber-reinforced resin layers of a first hoop layer and a second hoop layer, the two hoop layers (3A, 5A) have an overlapped portion, one end of the overlapped portion is located between 125 mm and 375 mm from the small-diameter end part of the shaft, and the other end of the overlapped portion is located between 675 mm and 925 mm from the small-diameter end part of the shaft.