A method for growing beta phase of gallium oxide (β-Ga2O3) single crystals from the melt contained within a metal crucible surrounded by a thermal insulation and heated by a heater. A growth atmosphere provided into a growth furnace has a variable oxygen concentration or partial pressure in such a way that the oxygen concentration reaches a growth oxygen concentration value (C2, C2′, C2″) in the concentration range (SC) of 5-100 vol. % below the melting temperature (MT) of Ga2O3 or at the melting temperature (MT) or after complete melting of the Ga2O3 starting material adapted to minimize creation of metallic gallium amount and thus eutectic formation with the metal crucible. During the crystal growth step of the β-Ga2O3 single crystal from the melt at the growth temperature (GT) the growth oxygen concentration value (C2, C2′, C2″) is maintained within the oxygen concentration range (SC).