A surveying instrument comprising: a monopod installed on a reference point, a surveying instrument main body provided at a known distance from a lower end of said monopod and at a known angle with respect to an axis of said monopod and having a reference optical axis, and an operation panel provided on said monopod and having a display unit, wherein said surveying instrument main body includes a measuring unit for irradiating a distance measuring light, for receiving a reflected distance measuring light and for measuring a distance to an object to be measured, an optical axis deflector for deflecting said distance measuring light with respect to said reference optical axis, a projecting direction detecting module for calculating a deflection angle of said distance measuring light with respect to said reference optical axis, a measuring direction image pickup module for acquiring an observation image (81, 84, 86), which includes said object to be measured, in a predetermined relationship with said reference optical axis, an attitude detector for detecting a tilt of said surveying instrument main body with respect to the horizontal, and an arithmetic control module for making said measuring unit perform a distance measurement along a predetermined scan pattern, and wherein said arithmetic control module performs image pickups of said object to be measured by said measuring direction image pickup module and scannings of said object to be measured by said distance measuring light using a closed loop scan pattern (83, 85), before rotation (that is, at the start of a measurement) and after rotation of said surveying instrument main body around said reference point after the start of the measurement, respectively, and said arithmetic control module carries out a general matching of said observation image acquired before rotation and said observation image acquired after rotation, judges whether intersections exist in a locus of said scan pattern acquired before rotation and a locus of said scan pattern acquired after rotation based on said matching image, sets said intersection as a cross point, obtains a deflection angle of said cross point with respect to said reference optical axis before rotation by said projecting direction detecting module, obtains a deflection angle of said cross point with respect to said reference optical axis after rotation by said projecting direction detecting module, and calculates a rotation angle of said surveying instrument main body based on a deviation between both of said deflection angles as obtained. and said arithmetic control module carries out a general matching of said observation image acquired before rotation and said observation image acquired after rotation, judges whether intersections exist in a locus of said scan pattern acquired before rotation and a locus of said scan pattern acquired after rotation based on said matching image, sets said intersection as a cross point, obtains a deflection angle of said cross point with respect to said reference optical axis before rotation by said projecting direction detecting module, obtains a deflection angle of said cross point with respect to said reference optical axis after rotation by said projecting direction detecting module, and calculates a rotation angle of said surveying instrument main body based on a deviation between both of said deflection angles as obtained.