The adsorption ability of dyes on chitin, a natural polymer was investigated for decolorization of dye wastewater. Chitin was manufactured in lab by decalcification in dilute aqueous HCl solution and deproteination in dilute aqueous NaOH solution with shrimp shells. Absorbance of residue solution of dyebaths after dye adsorptions of chitin were measured in varieties of dye concentration and dipping periods. Four kinds of dyestuffs were used, C.I.Acid Blue 29, C.IDirect Blue 6, C.I.Reactive Orange 12 and C.I.Basic Red 18. When chtin ig was dipped in 0.05% of dyebath with stirring, maximum adsorption ratio of each kind of dyes was exhibited as 91.6% for C.I.Acid Blue 29, 95% for C.I.Direct Blue 6, 58.2% for C.I.Reactive Orange 13 and 75.8% for C.I.Basic Red 18. It shows that chitin has better adsorption abilities of ionic dyes of acid, direct and basic dye than non-ionic reactive dye. And chitin has better adsorption abilities of anionic acid and direct dyes than cationic basic dye because of the presence of nitrogen atoms. All kinds of dyestuffs used showed speedy absorption effects by chitin, so chitin can absorb much amount of dyes in 5 mimutes reach to equilibrium of adsorption in 2 hours after dipping. Basic dye was absorbed the most speedily in 5 minutes, although maximum adsorption ratio is not high. That reason can be thought that chitin surface is essentially negatively charged due to polar funtional groups.