PROBLEM TO BE SOLVED: To provide a first agent for oxidative hair dye, which can dye even gray hair (that is, so that the L value of color difference is lower) and has a reduced harmful effect on hair feeling (for example, roughness of cuticle).SOLUTION: The present invention provides a first agent for oxidative hair dye, the agent comprising: (A) a surfactant; (B) a phosphate diester of an aliphatic alcohol having 8 to 30 carbon atoms; and (C) at least one fatty acid ester selected from the group consisting of isodecyl pivalate, isopropyl palmitate, and octyldodecyl myristate.SELECTED DRAWING: None