A volumetric measurement apparatus is provided which measures the volume of a liquid material stored within a container. The volumetric measurement apparatus includes a reference enclosure having disposed therein a single pressure sensor. The pressure sensor has a pressure sensitive element exposed to both internal spaces of the reference enclosure and the container to detect a pressure difference between the container and the reference enclosure. A sensor shielding member is arranged in the reference enclosure to selectively shield the pressure sensitive element from the internal space of the reference enclosure to detect only a pressure within the container. The volumetric measurement is made based on the pressure difference between the container and the reference enclosure and the pressure in the container.