[Problems] To provide an ion exchanger having excellent electric properties, a low electric resistance, excellent mechanical strength and, at the same time, having excellent contamination resistance.[Means for Solution] An ion exchanger comprises a melt-extrusion-formed body of a resin composition containing a granular ion-exchange resin and a low-melting polyolefin resin having a melting point of not higher than 170° C., the melt-extrusion-formed body: (a) containing the granular ion-exchange resin at a ratio of not less than 30% by weight but less than 50% by weight, and the low-melting polyolefin resin in an amount of more than 100 parts by weight but not more than 150 parts by weight per 100 parts by weight of the granular ion-exchange resin; (b) having a melt index in a range of 1 to 5 g/10 min. as measured at 190° C.; and (c) having a water content of not less than 30%.