An apparatus for growing single crystals of III-V compound semiconductors of the vapor pressure control type using a vertical puller characterized by dividing the surface area of a melt into two sections, covering one section with a liquid encapsulant while maintaining the other section in contact with the atmosphere of the vessel (furnace). The apparatus comprises a sealable vessel, an upper shaft, a lower shaft, a plurality of heaters, a crucible and a means for dividing the surface of the melt contained in the crucible. As a result, single crystals of III-V compound semiconductors having various excellent properties such as low impurity content (high purity), low dislocation density and the like maybe obtained.