PURPOSE: To obtain a hair dye agent for human hair, shortened in time required for dyeing, capable of providing natural handle to hair and, simultaneously, exhibiting durability hardly removing even in washing hair and capable of safely using because of characteristic hardly causing dermatopathy.

CONSTITUTION: This hair dye agent is obtained by mixing a methacrylic resin, an organic solvent, a gelling agent and an acidic dye with water and its pH is controlled to 1.5-5.0.