PURPOSE: To provide a method for producing a single crystal reduced in the content of impurities and in the change of the composition in the vertical and diameter directions by arranging a specific two element compound semiconductor in the high temperature region of a sealed tube and also arranging the third element single substance in its low temperature region.

CONSTITUTION: A two element compound semiconductor 2 comprising the first element (A) having a higher equilibrium dissociation pressure and the second element (B) having a lower equilibrium dissociation pressure is arranged in a crystal growth chamber 10 disposed in the high temperature region of a sealed tube 1, and also the third element single substance (C) or the mixture 4 of the component C with the component A is arranged in a receiving chamber 11 used for controlling the pressure of vapors and disposed in the lower temperature region. The high temperature region is kept at a higher temperature than the melting point of a three element mixed crystal compound semiconductor (D), and the low temperature region is also kept at a temperature which is lower than the melting point of the component D and higher than a temperature at which the saturated vapor pressure of the third element in an equilibrium state with a liquid phase equilibrated with a solid phase at the melting point of the component D is equal to the saturated vapor pressure of the component C and a temperature at which the saturated vapor pressure of the component A is equal to the saturated vapor pressure of the single body of the component A. The semiconductor 2 is thus melted, controlled so that the temperature of the upper surface center of the melted liquid is lowest, and subsequently gradually cooled.