To obtain the subject new compound retaining excellent adsorption ability to a metal due to not being subjected to crosslinking treatment, being insoluble even in an acidic solution, useful as a metal adsorbent, containing thiourea as a ligand.

This chitosan derivative is expressed by the formula (R is methyl, ethyl or phenyl). The compound of the formula is obtained, in the case of a methylthiourea derivative in which R is methyl group, by treating an amino group bonded to the C2 position of chitosan with methyl isothiocyanate, in the case of an ethylthiourea derivative in which R is ethyl group, by treating an amino group bonded to the C2 position of chitosan with ethyl isothiocyanate and, in the case of a phenylthiourea derivative in which R is phenyl group, by treating an amino group bonded to the C2 of chitosan with phenyl isothiocyanate. The chitosan derivative can be used for industrially recovering a metal such as gold, platinum, palladium, mercury, or the like.