To provide a method for producing 1,3,6-hexanetricarboxylic acid and/or its salt with reduced discoloration from 1,3,6-tricyanohexane obtained by an electrolytic reducing reaction of acrylonitrile according to simple and industrial treating procedures.

This method for producing the 1,3,6-hexanetricarboxylic acid and/or its salt is carried out as follows. A trinitrile mixture consisting essentially of the 1,3,6-tricyanohexane is separated from an electrolyte consisting essentially of adiponitrile and obtained by the electrolytic reducing reaction of the acrylonitrile. The 1,3,6-tricyanohexane in the mixture is hydrolyzed to provide a tricarboxylic acid or its salt or both which are then treated with an oxidizing agent.