A clamping apparatus comprising: a locking member protruding toward a leading end side relative to a housing and configured to be insertable into a hole of a to-be-clamped object; an advancing means pushing the locking member toward the leading end side with a predetermined force; a clamp rod including a wedge surface configured to make an engagement with the locking member from the leading end side; and a driving means configured to drive the clamp rod toward a base end side for clamping and configured to drive the clamp rod toward the leading end side for unclamping, the locking member comprising: a base portion configured to be inserted into the hole; and a protruding portion provided on the leading end side relative to the base portion, and configured to come to face a peripheral wall of the hole when the locking member is moved to a radially outside diameter-expanded position, the clamping apparatus further comprising a relative movement restriction mechanism configured to restrict movement of the clamp rod toward the base end side relative to the locking member within a predetermined travel distance in such a manner that movement of an outer peripheral surface of the base portion toward the base end side relative to an inner peripheral surface of the hole is allowed when the locking member is in the diameter-expanded position, characterised by a guide member supporting the locking member so that the locking member is movable radially, the guide member protruding toward the leading end side relative to the housing so as to be insertable into the hole of the object, wherein the relative movement restriction mechanism is disposed between: a base-end-side portion of the guide member that is on the base end side; and the clamp rod. a locking member protruding toward a leading end side relative to a housing and configured to be insertable into a hole of a to-be-clamped object; an advancing means pushing the locking member toward the leading end side with a predetermined force; a clamp rod including a wedge surface configured to make an engagement with the locking member from the leading end side; and a driving means configured to drive the clamp rod toward a base end side for clamping and configured to drive the clamp rod toward the leading end side for unclamping, the locking member comprising: a base portion configured to be inserted into the hole; and a protruding portion provided on the leading end side relative to the base portion, and configured to come to face a peripheral wall of the hole when the locking member is moved to a radially outside diameter-expanded position, the clamping apparatus further comprising a relative movement restriction mechanism configured to restrict movement of the clamp rod toward the base end side relative to the locking member within a predetermined travel distance in such a manner that movement of an outer peripheral surface of the base portion toward the base end side relative to an inner peripheral surface of the hole is allowed when the locking member is in the diameter-expanded position, characterised by a guide member supporting the locking member so that the locking member is movable radially, the guide member protruding toward the leading end side relative to the housing so as to be insertable into the hole of the object, wherein the relative movement restriction mechanism is disposed between: a base-end-side portion of the guide member that is on the base end side; and the clamp rod.