The present invention is completed by finding that a silver ion-containing zirconium phosphate represented by the following formula (1) is excellent in heat resistance and chemical resistance, low in resin coloring and excellent in processability.AgaMbZrcHfd(PO4)3.nH2O (1)wherein, in the formula (1), M is at least one ion selected from alkali metal ion, hydrogen ion and ammonium ion, a, b, c and d are positive numbers satisfying a+b+4(c+d)=9 c and d satisfy 1.75<(c+d)<2.25 and n is 0 or a positive number of not more than 2.
