A heat flux measurement apparatus 100 includes a first measurement unit 110, a second measurement unit 120, and heat flux calculation units 130, 140. The first measurement unit 110 measures a temperature difference between a first measurement location and a second measurement location that is lower in temperature than the first measurement location, using a thermocouple 112. The second measurement unit 120 measures a temperature difference between a third measurement location that can be assumed to be isothermal with the first measurement location and a fourth measurement location that can be assumed to be isothermal with the second measurement location, using a thermocouple 122 different in time constant from the thermocouple 112. The heat flux calculation units 130, 140 use measured temperature differences respectively acquired from thermal electromotive forces of the thermocouples 112, 113 of the measurement units 110, 120, and time differential values of the actual measured temperature differences of the respective measurement units 110, 120 to detect a time constant of the thermocouple 112, 122 of at least one of the measurement units 110, 120, calculate a compensated temperature difference by compensating a response lag of the actual measured temperature difference by the detected time constant, and calculate a heat flux based on the compensated temperature difference.