A variable compression ratio apparatus may include a cylinder block and a mounting hole formed at a side surface thereof; a connecting rod pivotally connected to the piston; a crankshaft provided with a central axis, a bearing seat coaxially disposed with the central axis, and a crank pin formed in a crank arm connecting the bearing seat with the central axis of the crank pin eccentrically, wherein the crank pin is rotatably connected to the connecting rod; and an eccentric bearing provided with a bearing central axis and a crank mounting hole formed eccentrically to the bearing central axis, the crank mounting hole of the eccentric bearing being rotatably coupled to the bearing seat rotatably inserted in the crank mounting hole, wherein the eccentric bearing changes the compression ratio by controlling a distance between the central axis and a combustion chamber according to driving condition of the vehicle.