We present the fabrication and the performance of a micro-thermoelectric hydrogen gas sensor built with a thermopile composed of 18 thermocouples on a dielectric thin membrane. Every thin film thermocouple is a pair of Au- and boron-doped Si0.8Ge0.2 thin films deposited by sputtering with the thickness of 200 and 300 nm, respectively. The gas detection of the sensor is triggered by the catalytic combustion of hydrogen and the thermopile converts the combustion heat to electric voltage and current. The performance of the device is studied with respect to the design of the heater, the thermopile, and the catalyst on the membrane. The sensor-device with the thermopile is also compared to a sensor with a single thermoelectric couple. The device built with the thermopile shows 11-fold amplification voltage signal and a thermopower 15 times than the single thermoelectric line device.