A liquid trap device for a gas is provided which includes a trap housing (3) that is formed from a ceiling wall (5), a bottom wall (6) and a peripheral wall (7), the ceiling wall (5) having provided therein a gas inlet port (20) and a gas outlet port (21), and a filter element (4) that is retained between the ceiling wall (5) and the bottom wall (6), the interior of the filter element (4) communicating with the gas inlet port (20) and the outer peripheral face of the filter element (4) communicating with the gas outlet port (21) via an internal space (8) of the trap housing (3), wherein the trap housing (3) is formed as a shape that in plan view is long along one laterally central line (X), and the filter element (4) and an outlet port upstream portion (21a), opening within the trap housing (3), of the gas outlet port (21) are disposed in proximity to first and second side wall portions (7a, 7b) respectively of the peripheral wall (7) facing each other on the laterally central line (X). This enables a liquid trap device for a gas to be provided in which a sufficient lateral distance from a filter element to a gas outlet can be guaranteed while having small dimensions and the performance in capturing a liquid can be enhanced.