An air conditioning system having an inlet air temperature calculating block that calculates a variation in air temperature at an inlet port of each unit based on position information and also calculate the air flow rate through each unit. A temperature sensitivity calculating block calculates temperature sensitivity of each unit obtained by dividing the variation in air temperature at the inlet port by a variation in air temperature at an outlet port of each unit. An inlet air temperature calculating block calculates the air temperature at the inlet port of each unit on the basis of the air temperature at the outlet port of each unit, and the temperature sensitivity.