A flammable gas concentration detection apparatus (1) including an energization control unit (50) that switches the energization state of heating resistor (34) at regular time periods TW, and a gas concentration computation unit (7). The heating resistor has first and second set temperatures CH and CL. The voltage detected across the heating resistor at the first and second set temperatures corresponds to a high and low temperature voltage, respectively. The gas concentration computation unit computes the concentration of a flammable gas based on a first information group including an average high temperature voltage averaging the values of two temporally successive high temperature voltages, the low temperature voltage in a period of time between two high temperature voltages, and an environment temperature in the period of time in which the low temperature voltage is detected.