NOVELTY - A metal adsorbent comprises polyallyl amine derivative containing polyallyl amine and isothiocyanate which has repeating unit containing thiourea group and amino group by which one hydrogen atom is substituted by isothiocyanate. The molar ratio of thiourea group and amino group of polyallyl amine derivative is 5-20:95-80.    USE - Metal adsorbent for metal adsorption (claimed). Can also be used for purification of wastewater, efficient exploitation of resources, recovery of palladium catalyst for recycle of rare metal from disposable household electric appliances products, recovery of platinum for fuel cells, and recovery of catalyst for synthesis of pharmaceutical, organic electronics material and electronic substrate of mobile telephone, recovery of rare metal from seawater and waste industrial waters, and recovery of poisonous metal in environment.    ADVANTAGE - The metal adsorbent has high adsorptivity with respect to rare metal.    DETAILED DESCRIPTION - A metal adsorbent comprises polyallyl amine derivative containing polyallyl amine and isothiocyanate which has repeating unit of formula -(CH2-CH(CH2-R1))- containing thiourea group and amino group by which one hydrogen atom is substituted by isothiocyanate. The molar ratio of thiourea group and amino group of polyallyl amine derivative is 5-20:95-80.    R1=thiourea or amino of formula -NH-C(=S)-NH-R2; and    R2=1-5C linear or branched alkyl, 6-10C aryl or 7-10C aralkyl.    INDEPENDENT CLAIMS are included for:    (1) manufacturing method of metal adsorbent involving adding isothiocyanate to solution containing polyallyl amine and mixing, and manufacturing polyallyl amine derivative which has thiourea group and amino group by which one hydrogen atom is substituted by isothiocyanate; and    (2) metal adsorption method involving preparing metal salt aqueous solution obtained by dissolving metal, producing deposit of metal adsorbent by adding metal adsorbent to metal salt aqueous solution, separating metal salt aqueous solution into solid and liquid and collecting deposits.