The present invention relates to an apparatus for loading and unloading an LNG tank container, the apparatus comprising: a base provided at a place at which LNG is used; a transfer cart capable of moving back and forth with respect to the base; a clamping device provided at a head part of the transfer cart; and a clamp position adjusting device capable of adjusting a horizontal position of the clamping device. Since there is no transfer of the LNG between tanks, the amount of LNG loss is reduced and the risk for the occurrence of a fire accident is reduced.