A surveying instrument comprising; a horizontal rotating unit, a measuring unit installed on the horizontal rotating unit, a coupler for mechanically removably coupling said horizontal rotating unit with said measuring unit, and a connector for electrically connecting said horizontal rotating unit with said measuring unit, wherein said coupler comprises a lower coupling element to be fixed on an upper surface of said horizontal rotating unit and an upper coupling element to be fixed on a lower surface of said measuring unit, and said lower coupling element and said upper coupling element are fitted and coupled, and wherein said connector is designed in a separable structure and when said measuring unit is mechanically mounted on said horizontal rotating unit, said connector electrically connects said measuring unit and said horizontal rotating unit, wherein said horizontal rotating unit comprises a driving unit for rotating said measuring unit, a horizontal angle detector for detecting a horizontal angle, and a horizontal angle control unit for calculating horizontal angle data based on a signal from said horizontal angle detector and for controlling said driving unit, wherein said measuring unit comprises a distance measuring unit for performing a distance measurement, a vertical angle detector (26, 53), a vertical angle control unit for calculating vertical angle data based on detection results from said vertical angle detector, a coordinate calculating unit, and a main control unit, wherein said horizontal angle control unit transmits the horizontal angle data at the time of distance measurement to said coordinate calculating unit via said connector based on a control signal from said main control unit and distance measurement data by said distance measuring unit and said vertical angle data from said vertical angle control unit are inputted to said coordinate calculating unit, and said coordinate calculating unit is constituted so as to calculate three-dimensional data based on said horizontal angle data, said distance measurement data and said vertical angle data, wherein said measuring unit is a two-dimensional scanner unit or a sighting distance measuring unit, wherein said two-dimensional scanner unit comprises said distance measuring unit for emitting a pulsed distance measuring light and for performing distance measurement per each said pulsed distance measuring light, a scanning mirror provided on a vertical rotation shaft having a horizontal axis and for rotatably irradiating said pulsed distance measuring light, a motor for rotating said vertical rotation shaft, wherein said vertical angle detector detects a rotation displacement of said scanning mirror, wherein said two-dimensional scanner unit is constituted so as to acquire two-dimensional point cloud data based on the distance measurement result of said distance measuring unit and on the rotation displacement at the time of distance measurement as detected by said vertical angle detector, said two-dimensional point cloud data are inputted to said coordinate calculating unit and three-dimensional point cloud data are calculated by said coordinate calculating unit, wherein said sighting distance measuring unit comprises a telescope unit rotatable in a vertical direction, a motor for rotating said telescope unit in a vertical direction, and said vertical angle detector detects a vertical angle of said telescope unit, wherein said telescope unit has a sighting telescope and said distance measuring unit, said distance measuring unit performs distance measurement of said measuring point under a condition where a predetermined measurement point is sighted by said sighting telescope, said vertical angle control unit calculates vertical angle data of said sighting telescope under a sighted condition, and distance measurement data and said vertical angle data based on the distance measurement result of said measuring point are inputted to said coordinate calculating unit.