PURPOSE: To male low fuel consumption compatible with high output by simplifying the structure, restraining the increase in costs and extending the degree of freedom of the layout, in a valve device fo an internal combustion engine.

CONSTITUTION: A cam contact part 14 to come in contact with a cam 16 is movably provided to a rocker arm 12 along the rotational direction of the cam 16, the cam contact part 14 is formed by a high speed rotating slipper part 14a formed into an circular shape in section and a low rotating slipper part 14b formed into a circular shape in section, and having the diameter smaller than the high rotating slipper part 14a. And a cylinder part 20 is formed inside the rocker arm 12, and a protruded part 19 provided on the lower part of the cam contact part 14 is arranged on the cylinder part 20, and a piston 21 to come in contact with the protruded part 19 is arranged. And a return spring 22 is arranged on the cylinder part 20 in which one end side of the piston 21 is positioned, and an oil pressure passage 23 is connected to the cylinder part 20 in which the other end side of the piston 21 is positioned.