PURPOSE: To subject an electrode formed on a semiconductor substrate to a heat treatment sufficiently by a method wherein only the specific part including a part where the electrode is formed is heated by a heating laser beam source.

CONSTITUTION: A semiconductor substrate S is placed on the sample table of a heat treatment furnace with a p-type side electrode 57 facing upward. It is observed by a microscope whether the scanning pattern of a laser beam is aligned with the part where the p-type side electrode 57 is brought into contact with a p-type GaAs cap layer 55 or not. If it is not aligned, an operation table is driven to correct the scanning position. After the alignment of the laser beam application position is finished, a heating start instruction is inputted to a controller by the operation table. The controller switches the output of an argon gas laser device from low to high in accordance with the instruction and the part where the p-type side electrode 57 is brought into contact with the p-type GaAs cap layer 55 is scanned by the laser beam spot light A and heated. By this heating, the p-type side electrode 57 is brought into ohmic contact with the p-type GaAs cap layer 55.