A thermoelectric device consisting of the porous part and the bulk part was proposed. Increase of heat exchange area due to porous medium will improve the efficiency of heat exchange between heating/cooling sources and the device. Estimation based on physical properties of FeSi2 indicated that generated power of the partially porous device per unit area can be several times higher than that of the bulk one in case of gas heating / cooling system. The partially porous thermoelectric devices were produced. In measurement of power, it has been confirmed that generated power per unit area of the partially porous FeSi2 devices was roughly 10 times higher than that of the conventional device. The proposed porous device will exhibit its advantage in the case of low heat transfer coefficient between the device and the heating / cooling sources.