PURPOSE: To stabilize joining strength by detecting the temperature of a joining part by using a temperature sensor, increasing heat energy of a heating means at a point of time when an integrated value of periods having this temperature higher than a first set temperature attains a specified value and increasing the temperature of the joining part up to the melting temperature of brazing filler metal.

CONSTITUTION: Heating of the joining part 2a is started by a burner part (heating means) 30. The temperature of the joining part is detected by the infrared temperature sensor 40. The heat energy of the heating means 30 is increased and the temperature of the joining part increases at a point of time t6 when the integrated value of the periods Ta, Tb and Tc having the temperature of the joining part higher than the first set temperature TM1 attains the specified value T1 and flux is molten sufficiently. Heating is stopped and brazing is completed at a point of time t8 when the temperature of the joining part attains a second set temperature TM2 higher than the first set temperature TW1 and the specified time T2 elapsed from a point of time t7 when the brazing filler metal is molten. Consequently, joining strength can be stabilized and strength decrease of base metals can be prevented by obviating excess and deficiency of heating of the joining part.