To provide a gas supply device which can supply by reducing pressure of compressed gas in stable condition and is superior to economical efficiency and safety.

The gas supply device, which supplies by reducing pressure of the gas supplied from a compressed gas supply source (high-pressure gas vessel 11) by pressure reducing means (pressure regulators 21, 31), it provided with heat exchangers 22, 32 heating up the gas by thermally exchanging the gas introduced in the pressure reducing means and hot water supplied from hot-water supply source (hot-water circulation unit 15) on the upstream side of gas flow direction of the pressure reducing means and at the same time a hot water flow passage 53 for heating up the pressure reducing means by means of a part of the hot water on the pressure reducing means.