To achieve a compound semiconductor thin film with improved film quality by growing a semiconductor thin film on a semiconductor substrate, without taking out the semiconductor substrate from a vacuum device after decomposing and eliminating an oxide film on the semiconductor substrate.

A structure, where a preparation chamber 1 and a growth chamber 2 are partitioned, is used more preferably as in a molecular beam epitaxy apparatus. In this case, a light-cleaning device 3 is mounted to the preparation chamber 1, a silicon substrate 4 is introduced to the preparation chamber 1, the preparation chamber 1 is evacuated and then is irradiated with vacuum ultraviolet rays, and an oxide film on the surface of the silicon substrate 4 is removed. At this time, the silicon substrate 4 need not be heated, and damages given to the silicon substrate 4 itself can be reduced. After that, a gate valve is opened, the silicon substrate 4 is moved to the growth chamber 2, and a compound semiconductor thin film is grown. Since the silicon substrate 4 can be moved in vacuum, no oxygen and other impurities will adhere, thus enabling growth of the compound semiconductor thin film with a clean surface.