Used in an apparatus for pulling a Si single crystal 36 up from Si molten liquid 35 by using the Czochralski method. In order to produce a Si single crystal having a desired quality, the diameter of the Si single crystal is controlled by controlling the pull-up speed of the Si single crystal, the sum of a reference temperature set value T.sub.B (X), which is a function of a pull-up distance X of the Si single crystal from a certain growth point, and a value proportional to a diameter deviation .DELTA.D is regarded as a reference temperature, and electric power supplied to a heater (24) for heating the Si molten liquid is controlled so that the temperature of the vicinity of the heater is equal to the reference temperature. In order to easily and quickly set the temperature pattern, various operational data in producing a Si single crystal is automatically collected and stored in a magnetic memory disk (82) corresponding to quality data of the Si single crystals which have been produced, data similar to the quality of a Si single crystal to be produced is retrieved from the stored data, an operator selects the most similar data, the selected operational data is displayed in a display unit (80), and the operator sets the reference temperature pattern T.sub.B (X) on a screen of the display unit by using a mouse (78).