A process for producing an amphoteric electrolyte resin by continuous bulk polymerization at low cost is provided. Also provided is an apparatus for achieving the process. The process comprises the steps of: feeding, from the mixture supply side, a mixture comprising 0.01 to 10 wt % of at least one radically polymerizable basic monomer containing a nitrogen atom, 0.01 to 35 wt % of at least one radically polymerizable acidic monomer having a carboxyl group and 45 to 99.98 wt % of a monomer capable of copolymerizing with these monomers.