Abstract: There is provided a sheet thickness and swell measurement method and apparatus to calibrate a characteristic map of a reference plane with accuracy and on demand, and to provide a simpler construction of means for creating the characteristic map of the reference plane and means for calibrating the characteristic map. Measurement heads 2 are moved to the width direction of sheet 9, and the thickness of the sheet is measured by the sheet thickness measurement sensors 3 installed in the measurement heads 2. The measured values of the sheet thickness are calibrated by a characteristic map MP of the moving mechanism 4 of the measurement head 2 with respect to the sheet width direction, which has been created in advance. Highly directional electromagnetic waves emitting means is arranged on one side of the main frame 1 for emitting highly directional electromagnetic waves 5a, such as light or beam, which define a reference plane for creating the characteristic map.