An apparatus of producing a semiconductor crystal comprising a reactor tube having an open end in at least one end side, formed of any one material selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, and aluminum oxide, or of a composite material with any one material selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, boron nitride, aluminum oxide, magnesium oxide, mullite, and carbon as a base, and having an oxidation-proof or airtight film formed on a surface of the base, heat means arranged around said reactor tube in the atmosphere, a flange attached at said open end to seal said reactor tube and a crucible mounted in said reactor tube to store a material of said semiconductor crystal.