The invention discloses an indigo purifying apparatus, comprising a body and an evaporating chamber arranged in the body. A discharge passage is arranged in the top inner wall of the evaporating chamber in communicated manner; a reaction chamber is communicated with the top of the discharge passage; a transition passage is communicated with the bottom of the evaporating chamber; a feeding chamberwhich opens rightward is arranged in the bottom of the transition passage in communicated manner; a heating barrel is arranged in the evaporating chamber; a heating chamber is arranged in the heatingbarrel; electric connection support blocks are embedded in the left and right inner walls of the evaporating chamber; an automatic butting mechanism electrically connected with the electric connectionsupport blocks are arranged in the left inner wall of the transition passage; a top pressure auto-discharge mechanism is arranged in the discharge passage; a first motor is embedded in the top innerwall of the reaction chamber; a rotating post is in power connection with the tail end of the bottom of the first motor; the outer surface of the rotating post is provided with a screw thread.