Abstract: The present invention relates to the manufacturing process of semi-insulating gallium arsenide single crystal by pulling a seed crystal contacted with gallium arsenide melt which is obtained by heat-reacting gallium and arsenic in a crucible contained in a pressure container and is characteristic in providing a film layer of 8-20 mm thickness of melted boron oxide with less than 200 ppm water content under pressure controlled at 60 kg/cm.sup.2 and over during reaction and at 5-40 kg/cm.sup.2 during crystal growth in high purity inert gas atmosphere, and during said crystal growth, rotating said seed crystal and said crucible in the same direction, but said seed crystal being rotated 5-30 rpm faster than the said crucible, and setting the crystal growing plane of said seed crystal to be within .+-.3.degree. from {100} plane.