Spray coating is performed utilizing a mixture of refractory material and a combustionable metal powder. The size of the particle of the metal in the mixture is selected so that the particle size is large enough to be treated safely and is small enough to be transported by means of a gas flow. As a carrier gas for carrying the mixture, a non-combustionable gas or fuel gas is used. A fuel gas and a combustion-assisting gas are discharged toward the section to be treated on the surface for directing a combustioning frame. The refractor material with the carrier gas is discharged into the frame established by the fuel gas and the combustion-assisting gas. The average size of the metal particle to be used in the spray coating is limited to be greater than 50 .mu.m. By enlarging the particle size of the metal, combustion of the metal particle becomes difficult. Combustion of such large particle size metal can be assisted by discharging the combustion-assisting gas together with the fuel gas. This compensates combustion efficiency to be dropped by utilizing the larger particle size metal.