PURPOSE: To provide a compression ratio varying device for internal combustion engine, with which changing-over of the compression ratio is obtainable certainly.

CONSTITUTION: The minor end of a connecting rod 6 is pivoted at a piston while the major end is pivoted on a crank shaft 1, and an eccentric sleeve 5 is rotatably installed in either of the connecting rod pivoted parts, and an eccentric sleeve lock means 11 is provided which can fix the rotation of the eccentric sleeve 5, and thus a compression ratio varying device for internal combustion engine is accomplished, wherein the sleeve 5 is fitted with brims 5', 5". The brims 5', 5" are arranged movable in a certain specified direction relative to the eccentric sleeve, and a friction clutch 53 is furnished to generate friction touch of the brims with the mating surface by pressing them to the mating surface on the crank shaft side.