An apparatus for mounting a battery cell mounts a battery cell stack to a frame that includes a base cover and a pair of side covers respectively extending from both ends of the base cover. The apparatus includes a support member to support the battery cell stack, a roller member around which a film fixed to the support member is wound, and a film guide member configured to move the film into the frame. When the film guide member moves the film into the frame, the support member and the frame move toward each other, and the battery cell stack is movable along the film to be mounted to the frame.