A method and low cost apparatus to accurately determine the gain, offset, and/or skew calibration values of each A/D converter in a few steps for an interleaving A/D converter. The calibration method includes: applying sine waves to the input as a calibration signal during calibration, A/D converting of the sine wave by a plurality of A/D conversion means in a predetermined order and storing the converted data in a data storage memory, and determining the gain, offset, and/or skew calibration values by using sine curve fitting on a sequence of converted data for each of the plurality of A/D conversion means.