To provide a deformation sensor, a calibration method and a program for calibration capable of reducing error due to strain of a sensor body.

A deformation sensor 1 includes a sensor body 22 that is elastically deformed and a control portion for calculating a detection value corresponding to the deformation amount of the sensor body 22; the control portion having a detection value comparison portion for comparing the detection value F30 at the time of earlier detection T8 to the detection value F23 at the time of later detection T9, which follows T8 in time sequence, and a calibration portion for calibrating the detection value F23 at the time of the later detection T9 in order to reduce error due to strain of the sensor body 22 at the time of the earlier detection if comparison between the two detection values shows that the detection value F23 at the time of the later detection T9 is smaller than the detection value F30 at the time of the earlier detection T8, with a change direction of the detection value F23 while the sensor body 22 is accumulating elastic force and deforming set as a positive direction.