Amperometric hydrocarbon sensor based on the oxygen pumping current was studied for monitoring hydrocarbon in exhaust gas. It was found that the oxygen pumping current through the sensor using La0.9Sr20.1Ga0.8Mg0.2O3 electrolyte at 1 V application monotonically increased with C3H6 concentration, but hardly depends on oxygen concentration when Pt and SnO2 were used for the active and the inactive electrode for oxidation, respectively. The oxygen pumping current of the developed sensor under 1 V application is hardly changed by coexisting CO and H2O. Consequently, the developed amperometric hydrocarbon sensor can detect hydrocarbon with high selectivity.