A variable compression ratio apparatus mounted on an engine may include an eccentric bearing assembly engaged with the piston through a piston pin, and including an eccentric ring having an eccentric hole so that the piston pin may be rotatably installed therethrough while being eccentric to the eccentric ring, and an eccentric link connected to the eccentric ring to transfer rotation force to the eccentric ring, a first connecting rod rotatably installed at an one side in an axial direction of the eccentric ring, a second connecting rod rotatably installed at the other side in the axial direction of the eccentric ring, and a control shaft connected to the eccentric link to rotate the eccentric bearing assembly by transferring the rotation force to the eccentric ring.