The pulley structure (1) of the present invention includes a ventilation path (10) that is formed at a position shifted in a radial direction from a rotating axis of a first rotating body (2) and allows a spring accommodation space (8) formed between the first rotating body (2) and a second rotating body (3) and the outside to communicate with each other. At least a part of the ventilation path (10) is formed in an end cap (5) that blocks an opening portion (21) on one side of the first rotating body (2) in a rotating axis direction. The end cap (5) blocks the opening portion (21) of the first rotating body (2) such that the spring accommodation space (8) does not communicate with the outside toward the one side in the rotating axis direction other than the ventilation path (10).
