The input rotation speed of an automatic transmission is fixed, and an output shaft is fixed. Oil pressure supplied to a measurement subject engagement element is then increased, and a determination is made as to whether or not rotary variation in a turbine rotation speed is equal to or greater than a set value. When the rotary variation reaches or exceeds the set value, an oil pressure controlled variable at this time is measured and stored. Then, on the basis of the measurement data, a correction amount relating to the unique characteristic variation of the automatic transmission incorporated into a vehicle body is determined and written to a TCU.