Disclosed is a gas generation device 100 that has a mist trap 50a equipped with a tubular housing 51, a gas inlet port 52 for allowing the gas generated from an electrolytic cell, a gas outlet port 53 for allowing the gas to flow out of the housing, a filler receiving section 58 that is positioned between the gas inlet port 52 and the gas outlet port 53 and receives a filler 56 for adsorbing mist and microparticles, and a gas diffusion section 57 that is positioned between the gas inlet port 52 and the filler receiving section 58 and is for diffusing the gas generated from the electrolytic cell 1 through the housing 51, that the gas outlet port 53 has a gas inlet tube 55 connecting to the interior of the housing 51, and that a gas entry portion 59 of the gas inlet tube 55 is arranged so as to be embedded in the filler 56 received in the filler receiving section 58.