The inner surface shape measurement device, which measures an inner surface shape of a small hole formed in a workpiece, includes: a rotating body for rotating the workpiece around a rotation axis, and a linear-and-tilting-motion stage; an elongated probe capable of being inserted into the small hole of the workpiece; a probe linear-and-tilting-motion mechanism capable of adjusting posture of the probe; a camera, configured to be rotatable integrally with the rotating body, for imaging the probe from at least three circumferential positions on a rotation trajectory centered on a rotation axis; and a controller for adjusting the posture of the probe using the probe linear-and-tilting-motion mechanism based on an image taken by the camera at each of the circumferential positions.