A pointing axis estimation apparatus capable of removing pointing axis variations caused by factors other than pointing axis variations of a telescope, thereby estimating true pointing axis variations of the telescope. The pointing axis estimation apparatus includes: a laser light source-unit attitude detector for calculating translational and rotational displacements of a laser light source unit; an optical axis detection-unit attitude detector for calculating translational and rotational displacements of an optical axis detection unit; a pointing axis calculator for calculating a pointing axis based on information from an optical axis variation detector; and a pointing axis variation estimator for calculating a true pointing axis variation of a telescope based on displacement data output from the detectors and the calculator.