A series of thermoresponsive polymer gel electrolytes (PGES) based on poly(N-isopropylacrylamide) in aqueous potassium chloride was synthesized by radiation-induced polymerization and gelation using gamma rays from a Co-60 source. The electric conductivity and swelling properties of the PGE were determined as a function of temperature. It was found that the electric conductivity of the PGE depended strongly on the swelling ratio; most notably, it changed drastically near the volume phase-transition temperature of the PGE. The temperature/conductivity profile of the PGE exhibits a maximum peak at a certain temperature that is defined as the maximum conductivity temperature (T-max). The T-max of all of the PGEs prepared by low-dose irradiation agreed with the temperature, near the end of the volume phase transition, where the PGE was completely shrunken. Consequently, the conductivity of gels should provide a good method with which the totally shrunken temperature of the thermoresponsive gels can be monitored with good temperature precision.