A variable compression ratio apparatus for varying a compression ratio, may include a connecting rod that is connected to a piston to take a combustion force; a pin link, one end of which is eccentrically connected to a crankshaft and the other end of which is pivotally connected to the connecting rod to form a connection portion therebetween; a slot link including a control slot to receive and guide the connection portion along the control slot; and a driving unit coupled to the slot link and configured to move the control slot to control a position of the connection portion.