Abstract: The rotary drum of reactivation apparatus has spaced-apart helical electrodes disposed in mutually interposed helical state and fixed to the inner wall surface of the drum, these electrodes functioning upon rotation of the drum to propel by screw action active carbon from an inlet end to the other outlet end of the drum as electric power is supplied to the electrodes to cause electric discharge therebetween and conduction through the carbon, which is thereby subjected sequentially to drying, firing, and reactivation as a result of electric discharge effect and the resulting joule heat. Flow of excessive current between the electrodes is prevented by a constant-current circuit in the electric power supply system. Steam can be additionally injected against the carbon to promote the reactivation thereof.