To provide a raw material gas feed system which can efficiently feed a large quantity of low vapor pressure raw materials in which vapor pressure is relatively low, and which are hard to be evaporated, and can improve throughput in a gas use system.

In the raw material gas feed system where raw material gas is fed to a gas use system 4 in a pressure-reduced atmosphere, the system comprises: a raw material tank 40 storing raw materials 42 forming raw material gas; a raw material passage 48 in which one end is connected to the gas use system and the other end is connected to the raw material tank; and a charging pump means 50 installed in the middle of the raw material passage, promoting the flow of the raw material gas, and making the pressure on the upstream side in the raw material passage lower than that on the downstream side.