To provide a liquefied gas supply device improved in stability of gas supply by restricting lowering of the pressure inside a container with a temporary increase of the supply amount of a vapor phase liquefied gas inside the container.

This liquefied gas supply device includes: a gas pipe 7 communicated with a vapor phase part inside the container 3 housing the liquefied gas; a pressure sensor 11 for detecting the pressure of the vapor phase liquefied gas, which flows into the container or the gas pipe; a heat source machine 17 provided in a heater 13 for heating the liquefied gas inside the container to heat a heat medium flowing inside a heat exchanging pipe 25; a temperature sensor 29 provided in the heater 13 to detect the temperature of the heat transmitting medium 27; a heat medium pipe 19 for leading a heat medium from the heat source machine 17 to the heater 13; and a control section 21 for controlling heating of the liquefied gas inside the container. The control section controls the heat source machine 17 to heat the heat medium or to stop the heating in response to the pressure detected by the pressure sensor 11, and increases the heating amount of the heat medium by the heat source machine 17 when the temperature detected by the temperature sensor 29 is lower than a set temperature.