A variable compression ratio apparatus may include a connecting rod having a small end portion having an eccentric bearing installation hole, a large end portion rotatably connected to the crank shaft, and a space portion formed in a longitudinal direction of the connecting rod and communicated with the eccentric bearing installation hole, a piston pin fixedly, an eccentric bearing rotatably engaged to the eccentric bearing installation hole and coupled to the piston pin through a pin installation hole of the eccentric bearing, wherein the piston pin may be offset from a center axis of the eccentric bearing, an eccentric link connected to the eccentric bearing, a variable link rotatably connected to the eccentric link, a control link rotatably connected to the variable link, and a control shaft provided in the control link to rotate the control link, wherein the eccentric link may be rotated within the space portion.