PURPOSE: To obtain a plasma thermal spraying apparatus excellent in controllability of film thickness and film quality.

CONSTITUTION: In the plasma thermal spraying apparatus, plasma arc discharge 3 is measured by means of an instantaneous emission spectroscope 6 and analysis is done in an analysis and control section 7, and the changes in the amount of thermal spraying base material supplied and the flow rate of carrier gas are detected from plasma arc discharge intensity ratio between the thermal spraying base material and the carrier gas. Further, feedback signals are formed on the basis of the detected results in the analysis and control section 7 and feedback is applied to the bady 1 of the plasma thermal spraying apparatus, by which controllability can be improved.