This paper describes the measurement of temperature distribution in EDM arc plasma using spectroscopic analysis. The temperature distribution measurement was achieved by using a lens system to magnify the image of the plasma and a mask to limit the plasma region to be observed. The fluxes of two different wavelength spectra radiated from the arc plasma were measured simultaneously with optical fibers and photomultipliers, after which the temperature distribution was computed from the radiant fluxes using the line pair method and Ablel's inversion. Also, the influences of machining conditions, such as electrode shape, gap distance and discharge current, on the temperature distribution were investigated.