According to a manufacturing method of a heat flux sensor, the heat flux sensor is sandwiched between a heater plate and a cooling unit. The heater plate is disposed on the first surface of the heat flux sensor, and the cooling unit is disposed on the second surface of the same. A heat radiation measurement plate is disposed on a surface of the heater plate opposite to the surface on which the heat flux sensor is disposed. According to this configuration, the temperature of the heater plate is controlled in an inspection process such that the heater plate is kept at an ambient temperature. This makes it possible to stabilize the temperature of the heater plate in a short time.