To provide a variable valve timing mechanism with a small number of parts, and having high durability.

The variable valve timing mechanism includes a rocker arm 13 having a working point side arm 11 facing a valve 7 so as to cover an operation part 6; and a drive piston 14 positioned on an extension of a shaft part 4, extending along the extension of the shaft part 4 so as to pierce the rocker arm 13, and having an end face facing the operation part 6. A relief hole 16 with an opening smaller than the operation part 6 and piercing the drive piston 14 without contact is formed in the working point side arm 11 of the rocker arm 13.