To supply the sufficient oil to a contact face with a valve stem end of an adjuster bolt, by installing a bypass on an oil passage from a shaft support face of an rocker arm to an adjuster bolt hole, and mounting an outlet of the bypass on an valve side opening of the adjuster bolt hole.

A bypass 11 is installed on an oil passage 4 from a shaft hole 2 externally fitted to a rocker shaft of a rocker arm 10, to an adjuster bolt hole 3. This bypass 11 is branched in front of the adjuster bolt hole 3, and is extended to a valve side in parallel with the adjuster bolt hole 3, and an outlet 12 of the same is located near a valve side opening of the adjuster bolt hole 3. When the oil feed amount of an oil pump is small, a temperature is low, and the viscosity of the oil is high at the start of an engine, or during the idling, the oil is flown out from the outlet 12 through the bypass 11, so that a contact face with a valve stem end 7 of an adjuster bolt 6 is effectively lubricated.