Provided is a method for growing a β-Ga 2 O 3 single crystal, which enables the production of a plate-like β-Ga 2 O 3 single crystal having high crystal quality. In one embodiment, a method for growing a β-Ga 2 O 3 single crystal employing an EFG method is provided, said method comprising the steps of: bringing a plate-like seed crystal (20) into contact with a Ga203 melt (12), wherein the plate-like seed crystal (20) comprises a β-Ga 2 O 3 single crystal having a defect density of 5x10 5 /cm 2 or less in the whole region; and pulling up the seed crystal (20) to grow a β-Ga 2 O 3 single crystal (25).