Provided is a substrate for epitaxial growth, which enables the improvement in quality of a Ga-containing oxide layer that is formed on a ²-Ga 2 O 3 single-crystal substrate. A substrate (1) for epitaxial growth comprises ²-Ga 2 O 3 single crystals, wherein face (010) of the single crystals or a face that is inclined at an angle equal to or smaller than 37.5° with respect to the face (010) is the major face. A crystal laminate structure (2) comprises: the substrate (1) for epitaxial growth; and epitaxial crystals (20) which are formed on the major face (10) of the substrate (1) for epitaxial growth and each of which comprises a Ga-containing oxide.
