To improve the water removal efficiency of a water separator for separating water by swirling the water in gas.

The water separator includes a gas inlet pipe 2; a swirling current generation element 3 formed in the inlet pipe; a disk-like trap cover 12 with a diameter larger than the inner diameter of the inlet pipe 2 and set downstream of the swirling current generation element 3; a trap part 6 having two trap cases 16 which are attached in series to the trap cover 12 and which are formed by integrally forming a cylindrical part 13 having a water draining region 18 with the same outer diameter as that of the trap cover, formed in a portion of the cylindrical wall, and communicated with the outside, a downstream side end wall part 14 downstream of the cylindrical part 13, and a cylindrical second folded part 15 communicated with the cylindrical part 13 downstream of the downstream side end wall part 14; and a water discharge mechanism formed in the outside of the water draining region 18. Owing to this configuration, formation of a welded portion in the trap part which generates the conventional cause of lowering the water removal efficiency can be avoided and the water removal efficiency is improved.