Effects of electrode and phase configurations on arc behavior and temperature distribution in a multiphase AC arc were successfully clarified. A high-speed video camera with band-pass filters were addressed to measure the arc. A multiphase AC arc is promising material processing technology owing to the characteristics of large high-temperature volume and high energy efficiency. The arc behavior was observed by imaging arc discharge with a high-speed camera in millisecond time scale. The temperature was conducted by Boltzmann plot method using two types of argon line emissions filtered by the band-pass filters. The obtained excitation temperature is high with a range of 7.0 x 10(3) to 1.3 x 10(4) K. The arc swing in front of electrode becomes wider and the temperature uniformity improves as the number of electrodes and phases increase. The characteristic time due to fluctuation of 12-phase AC arc was 1.4ms, which was sufficiently shorter than the residence time of raw material in the arc. The 12-phase AC arc is useful for material processing in terms of temperature uniformity and fluctuation time.