A strongly basic anion exchange resin of gel type having trimethylamine type quaternary ammonium groups and a cross-linked three dimensional polymer structure formed by copolymerization of a monovinyl aromatic monomer with a cross-linkable aromatic monomer, wherein the water content X (wt %) of the resin with counter ions being a standard type (chlorine type) and the salt-splitting capacity Y (meq/g-Resin) are in a relation represented by the following formula (1) or (2): Y.gtoreq.0.0214X+3.26 (1) provided 50