PURPOSE: To control the temperature of a room according to the intrinsic temperature characteristics of the culture base in the control of the culture base temperature in malt-preparation process.

CONSTITUTION: In a follow-up control of culture base temperature to a preset objective temperature A by controlling the room temperature a4, the indication room temperature a0 at the start of control is set to an arbitrary point according to the rising temperature characteristics intrinsic to the culture base. The indication room temperature a0 at the start of control is made to coincide with the preheating room temperature a3 of a malt-preparation room 1.