To enable the simultaneous cleaning work of an air sending means which has been performed separately from the cleaning of a solution tank in a prior art, and to simplify a time and labor.

Powder from a powder supply means 4 is supplied into a solution tank 1 via a supply port 3 formed at a canopy 2 of the upper part of the solution tank 1. A solution liquid is supplied into the solution tank 1 via liquid feed port 11, and when the powder is supplied into the solution tank 1, since air in the solution tank is exhausted via an exhaust passage 56, the steam of the solution liquid and the scattered powder are prevented from being intruded into the powder supply means 4. An air sending means 57 arranged at the exhaust passage 56 has a water proofing property, and when cleaning the solution tank 1, the cleaning liquid is made to overflow into the exhaust passage 56, and the air sending means 57 is also simultaneously cleaned.