The present invention provides an oxidation hair dye which comprises a first agent containing an alkaline agent and a second agent containing an oxidizing agent, said first and second agents being to be mixed together, characterized by, immediately after mixing the first agent with the second agent, said oxidation hair dye containing a bicontinuous microemulsion phase or a lamellar liquid crystal phase. The purpose of the present invention is to acquire an oxidation hair dye, which can exert a good dyeing effect on both damaged hair (hair chemically damaged by the use of hair dyes, perming agents, etc. and hair mechanically damaged by friction, etc.) and non-damaged healthy hair, by using a base agent that contains a bicontinuous microemulsion phase or a lamellar liquid crystal phase.
