Used in a Si crystal pulling apparatus using the Czochralski method, to lower the concentration of oxygen in the Si single crystal without increasing the production cost and to make the concentration substantially even all over the Si single crystal. The crystal 36 is produced by disposing a straightening tube 40 concentrically with and above a quartz crucible 22, letting inert gas flow down through the tube, dipping a seed crystal in Si molten liquid 28 in the quartz crucible and then pulling the seed crystal up. The concentration of oxygen in the Si single crystal is adjusted by controlling the distance H between the surface of the Si molten liquid and the bottom end of the straightening tube in accordance with the pull-up length Y or the pull-up time from a certain growth point of the crystal.