A highly selective and efficient biosorbent has been prepared from orange waste by introducing a phosphoric group at its polymer analog by simple chemical modification. Their adsorption behavior for several kinds of metal ions was studied and it was found to exhibit excellent selectivity towards several metal ions. As a typical example, a binary mixture of In(III) and Zn(II) was studied by using a packed column, indicating that In(III) ion can be selectively separated from its mixture with a concentration factor of 63 times. The maximum adsorption capacities evaluated in terms of mol/kg dry gel were 0.70 for In(III) and Ga(III), 0.97 for Cu(II), 1.15 for Pb(II) and Zr(IV), and 3.06 for Fe(III), respectively.