An automatic LPG tank insertion apparatus for automobiles has a rotary column provided with a lift body, which has a support arm. A rotating plate is rotatably mounted to the support arm such that yaw, pitch, and roll of the rotating plate can be controlled separately. Clamping devices are mounted on the rotating plate to selectively clamp an LPG tank. A trunk opening area measuring device includes a base unit, a guide shaft, a ruler shaft, and an encoder. Trunk opening sizes and LPG tank dimensions for various vehicle models are stored in a control computer. When vehicle model is input to the control computer, yaw, pitch, and roll of the rotating plate are adjusted so that the LPG tank can be inserted into a vehicle trunk.