To provide a pressure vessel adaptable to a high-pressure refrigerant like R410A or R410B, and moreover capable of being surely easily fitted to an installing surface like the bottom frame of an outdoor machine.

The following are integrally fitted: a cylindrical main body 2 extending in a vertical direction, an upper end closing member 3 for blocking the upper end of the main body 2, and a base seat member 10 for blocking the lower end of the main body 2 and also to be fixed to an installing surface 50. The upper end closing member 3 is formed into a neary semi-spherical state curved upward. The base seat member 10 has a lower end closing part 12 and a flange part 11. The lower end closing part 12 has a columnar state having a diameter neary same as that of the main body 2, is coaxially fitted to the main body 2, and is formed into a neary semi-spherical state wherein the end surface on the main body 2 side is curved downward. The flange part 11 extends outward in a diameter direction from the lower part outer periphery of the lower end closing part 12.