To provide an endless track belt with improved rigidity and durability as well as its manufacturing method.

In this endless track belt, a reinforcement core A is arranged in the peripheral direction of a endless track belt 4 with clearance in the width direction, with the rivet ratio of the reinforcement core A within a core layer 13 gradually increasing from the width center toward the width end; 0.55-0.65 at the width center and 0.75-0.95 at the width end of the endless track belt 4. Total denier of the reinforcement core A is 3000 d-15000 d. The twist coefficient K of the reinforcement core A is 1000-1700 (K = T√ D, where T = number of twists of cord (times/10 cm), D = total denier of cord). In manufacturing this endless track belt, the core layer 13 is established by spirally winding the reinforcement core A in the peripheral direction with clearance across the width from an end to the other end of the endless track belt 4. Also, the rivet ratio of the reinforcement core A within the core layer 13 is gradually increased from the width center toward the width end of the endless track belt 4.