MnO2 was immobilized in polyvinyl chloride membrane. A hydrogen peroxide sensor was set up by attaching the immobilized MnO2 membrane on top of a dissolved oxygen sensor of galvanic type. For comparison, sensors using catalase were also set up with immobilized catalase membrane or particles. The sensor was dipped in a certain volume of distilled water at a given temperature. Then, hydrogen peroxide aqueous solution of the fixed volume and concentration was added to the distilled water, and the response characteristics and stability of the sensor were investigated. The results obtained are summarized as follows. 1) It is found that the MnO2 membrane can be used as a membrane recognizing molecule for a hydrogen peroxide sensor. 2) The steady response value of these sensors is proportional to H2O2 concentration. 3) The response rate of the sensor using immobilized MnO2 membrane is the same as that of the sensor using immobilized catalase membrane. 4) When these sensors are stored in the distilled water at room temperature while not used, the sensor using MnO2 membrane shows stable response for more than three months.