An indium phosphide substrate for semiconductor devices is obtained as follows. In order to have the direction of growth of the crystal in the <100> orientation, a seed crystal having a specified cross-sectional area ratio with the crystal body is placed at the lower end of a growth container. The growth container housing the seed crystal, indium phosphide raw material, dopant, and boron oxide is placed in a crystal growth chamber. The temperature is raised to at or above the melting point of indium phosphide. After melting the boron oxide, indium phosphide raw material, and dopant, the temperature of the growth container is lowered in order to obtain an indium phosphide monocrystal having a low dislocation density and a uniform dopant concentration on the wafer as well as in the depth direction.