The present invention relates to a pyrolysis device using a liquid metal including: a hollow reactor in which the liquid metal is received; a circulating pump connected to the reactor; a buffer tank disposed on an upper portion of the reactor and receiving the liquid metal from the circulating pump; a nozzle coupled with the buffet tank and jetting the liquid metal within the buffer tank into the reactor; and an air supply source supplying air to the liquid metal within the reactor, wherein char generated from fuel injected into the reactor is combusted by reacting with air introduced into a lower portion” of the reactor through the air supply source, and liquid metal sprays jetted from the nozzle react with gases generated in the reactor to purify the gases.