A facile isolation of chitin from unutilized crustaceans such as crab shells was performed by direct extraction with an ionic liquid, 1-ally-3-methylimidazolium bromide (AMIMBr), followed by demineralization using citric acid. First, dried crab shells were treated with AMIMBr at elevated temperatures to extract chitin. Supernatants by centrifugation were then subjected to the chelating treatment with citric acid aqueous solution to occur demineralization and the precipitated extracts were isolated by filtration and dried. The X-ray diffraction, IR, and 1H NMR data of the isolated materials were identical with those of a commercial chitin. The degrees of deacetylation in the obtained samples were calculated on the basis of the IR spectra to be less than 7 %. Furthermore, the contents of proteins and the Mw values were less than 0.1 % and several hundred thousands, respectively.