A coating method of the invention is characterized by using particles each being an aggregate comprising particles far smaller than that, and heating them at a temperature lower than the melting point and blowing and depositing the same to an object to be treated at a supersonic velocity. The warm spray of the invention is characterized in that standard particles and addition particles with a particle diameter larger than that are mixed so that the K-value determined by the following relation is 1 or more and 2 or less: K=A×(B/C)×D, A: mass % of the content of additive particles, B: center particle diameter of standard particle (μm), C: center particle diameter of additive particle (μm), D: (maximum particle diameter−minimum particle diameter) of additive particle/10 (μm). The invention intends to deposit micro oxide crystals without using an adhesive or the like, with no alteration to the function thereof, and also attain a dense layer with no substantial voids.