PURPOSE: To provide a camshaft having a cam mechanism, with which a valve lift quantity of an engine is made variable, intake and scavenging efficiency higher than conventional is secured, and output performance can be enhanced.

CONSTITUTION: In an engine camshaft 1, a cam nose part 2b is formed separatable from a cam base circle part 2a, and an oil sump chamber 4 is equipped at a boundary between both the members. The oil sump chamber 4 is communicated with a camshaft journal part in an operation region of the cam nose part 2b. The cam nose part 2b is moved by hydraulic pressure in the radial direction of the camshaft 1 to change a cam nose projecting quantity so that a valve lift quantity can be varied.