To improve durability of a timing belt, and carry lubricating oil by the timing belt.

A timing belt 33 is provided with a belt shaped belt main body 41 and a plurality of inner gears arranged inside the belt main body 41 at a constant intervals, and a gear groove 43 engaged with an external gear of a timing pulley is formed between the inner gears 42 arranged adjacent to each other. A reinforcing liner 46 is embedded inside the gear groove 43. As a result, the deformation of the inner gear 42 is prevented by engaging with the external gear, and durability of the timing belt 33 is improved. A recessed part 53 is formed on the outer surface of the belt main body 41, and thereby, lubricating oil is carried by movement of the timing belt 33.