To obtain a glow discharge analyzer capable of measuring carbon contained in samples such as iron, steel, etc., in an extremely short time even through the use of an anode of material to which CO2, HC, etc., in the atmosphere are easily adhered.

A sample 29 is opposed to the tube part 15 of the anode 6 of a glow discharge tube 1. An inert gas IG is supplied for the surfaces of the sample 29 under low pressure. Then a high-frequency voltage or D. C. voltage is impressed between the sample 29 and the anode 6 to make glow discharge emit light, and the discharge emission is analyzed in a glow discharge analyzer. In this case, an inert gas supplying system P and a gaseous oxygen supplying system Q are parallelly connected to the glow discharge tube 1 so that gaseous oxygen may be supplied for the surfaces of the sample 29 from the gaseous oxygen supplying system Q together with an inert gas from the inert gas supplying system P at the time of preliminary discharge prior to analysis on one hand and that the supply of gaseous oxygen may be halted at the completion stage of the preliminary discharge.