PROBLEM TO BE SOLVED: To provide a method for controlling the temperature of a vegetation ground, by which the temperature of the ground can highly accurately be controlled from a ground temperature control-starting time, even when the measured value of ground surface temperature is not given as a boundary condition. SOLUTION: This method for controlling the temperature of the vegetation ground, characterized by disposing a weather datum-measuring apparatus comprising a heliograph, an outside air thermometer and an outside air hygrometer, disposing a memory for memorizing the weather data, performing a virtual heat transfer analysis on the basis of the historical measurement data memorized in the memory according to a time history ranged from a prescribed historical time to the present time, setting the determined ground surface layer region temperature at the present time as a temperature initial condition, hereafter performing heat transfer analyses on the weather data measured with the weather datum-measuring apparatus comprising the heliograph, the outside air thermometer and the outside air hygrometer, thus determining a ground surface layer region temperature in which an underground thermometer is not buried, and controlling a heat medium supplied to a pipe under the consideration of the heat conductivity of the ground, while using the underground temperature of the ground surface layer region as a target ground temperature.
