PURPOSE: To obtain a cosmetic for hair of head imparting stiffness to hair of head without tackiness nor starchiness by mixing a specific amount of a specific water-soluble, partially deacetylated chitin.

CONSTITUTION: 0.01-10wt.%, preferably 0.05-5wt.% water-soluble, partially deacetylated chitin having 40-60% deacetylated fraction and 10×104-100×104 average molecular weight is mixed into the objective cosmetic. Said water-soluble, partially deacetylated chitin is excellently adsorbed to hair and excellent in the membrane formability and the membrane is strong and able to impact a stiffness to hair. Natural chitin is hydrolyzed with alkali in 5-50% concentrated aqueous solution of alkali metal hydroxide at a temperature below 50°C in a homogeneous system, by suitably setting reaction temperature and reaction time to afford the above-mentioned active ingredient having a fixed average molecular weight and the deacetylated fraction.