To provide a roundness measuring device, a roundness measuring method, and a roundness measuring program, by which eccentricity can be found with high precision even if the eccentricity is large.

The roundness measuring device has a measurement acquisition part for acquiring as a measured distance a distance between a rotation axis O and the surface of a probe 24 on an X-axis connecting the rotation axis O and the probe 24 in detection by touching, and acquiring a rotation angle as a measured angle. Moreover the roundness measuring device includes: an eccentric position calculation part for calculating an eccentric distance e and an eccentric angle ; and a measurement correction part for correcting the measured distance so as to be a distance OP up to the rotation axis O from a contact point P where a work piece 4 and the probe 24 come in contact, based on the eccentric distance e, the eccentric angle , the measured angle , a radius R of the work piece 4, and a length (radius Rtip) from the center to the surface of the probe 24, and performs correction to add a correction angle between the X-axis whose center is the rotation axis O and the contact point P to the measured angle.