To efficiently cool a gas including powder, water droplet, etc.

A gas introduction opening 2 for introducing a gas which is to be cooled from tangential direction to the upper part, on peripheral wall, of a cylindrical main body part 1, a gas discharge pipe 3 which, with its lower end opened, projects into the main boy part from the center of a top plate, a discharge opening 4 of a main body part bottom plate, and a cooling coil 5 and a cooling jacket 6 for cooling the gas which is to be cooled flowing into the main body part, are provided.