A data processing method of variable measurement data in an electronic control unit (ECU) is provided. The ECU that processes the data processing method calculates a filtering frequency based on a delay time frequency based on a transmission timing cycle of the measurement data and a processing timing cycle of the measurement data in the ECU, and also based on a pulsation frequency of the measurement data, and removes, from the measurement data, a component of the filtering frequency calculated in the calculation of the filtering frequency.