To provide a thermal-electric power generation device which is a highly effective power generation system by burning rarefied gas, and to provide a heat-electric power generation method.

The thermal-electric power generation device 10 has a thermal- electric power generating medium composed of at least two pairs of porous thermal-electric power generation elements having electrodes 5, 6 and porous burning auxiliary parts 3, 4, having higher porosity than the thermal-electric power generating medium in a pair of intermediate parts of the thermal-electric power generating medium. Porosity of the porous burning auxiliary parts 3, 4 is 50% or higher and lower than 98%, and the device is constituted to pick up thermal-electric power generating output by the thermal-electric power generating medium by introducing combustible gas alternately in a predetermined period.