To provide a compression ratio variable engine having increased mounting rigidity of a subrod to a crank shaft, wherein a piston, a connecting rod the subrod, and a control rod are assembled to the engine precisely, while avoiding increase of a size of a crank case.

A crank cap is tightened to a pair of forked parts 71, 72 provided integrally on the subrod 68 so as to nip the other end part of the connecting rod 64 and one end part of the control rod 69 between them, respectively. Both end parts of a connecting rod pin 75 pressed into the other end part of the connecting rod 64 are turnably fitted into the forked part 71 on one side. Both end parts of a subrod pin 76 passing through one end part of the control rod 69 so as to turn relatively are fitted into the forked part 72 on the other side by clearance fitting.