To provide a high-load transmission belt having sufficient hardness to hardly cause cracking by repetitive bending, and improved bending resistance and heat resistance without rattling between a center belt and a block by using hydrogenated nitrile rubber in which aramid short fibers, nylon short fibers and carbon black are blended in a predetermined amount.

The high-load transmission belt 1 comprises a plurality of blocks 2 fitted and fixed to one another at predetermined pitches along the longitudinal direction of the center belts 3a, 3b. A rubber composition for each of the center belts 3a, 3b is formed so that 10-30 pts.mass short fibers and 50-70 pts.mass carbon black are blended in a 100 pts.mass highly-saturated copolymer obtained by partially hydrogenating a terpolymer of acrylonitrile-butadiene-carboxylate. The short fibers are composed of aramid short fibers and nylon short fibers, and the 5-15 pts.mass nylon short fibers are blended therein.