A surveying system comprising: a plurality of measuring units (3, 24, 59) and a leveling unit common to said plurality of measuring units, wherein said leveling unit has a cylindrical fitting hole and a notched recessed portion on an upper surface, and each of said plurality of measuring units has a fitting cylindrical portion (21, 52, 75) which is engageable with said cylindrical fitting hole, a fitting projecting portion (22, 53, 76) which is engageable and disengageable with respect to said notched recessed portion, a distance measuring component adapted to measure a distance to a target by emitting a distance measuring light, a horizontal angle encoder (9, 43, 74) adapted to detect horizontal angles, a vertical angle encoder (14, 47, 68) adapted to detect vertical angles, and an arithmetic control component (17, 49, 84), wherein said plurality of measuring units are constituted to be attachable and detachable with respect to said leveling unit respectively, each of said measuring units is selectively mounted on said leveling unit, and said plurality of measuring units are adapted to measure said target installed at a same reference position respectively, wherein, based on a measurement result of said target, one of said arithmetic control components is adapted to measure an azimuth angle offset amount which is a difference between a horizontal angle detected by the horizontal angle encoder of one measuring unit of said plurality of measuring units, when the target is measured by said one measuring unit and a horizontal angle detected by the horizontal angle encoder of another one measuring unit of said plurality of measuring units when the target is measured by said another one measuring unit and a machine height offset amount which is a difference between a height of the target calculated from a distance measurement of the target measured by the distance measuring component of said one measurement unit and a vertical angle of the target detected by the vertical encoder of said one measurement unit when the target is measured by said one measurement unit and the height of the target calculated from a distance measurement of the target measured by the distance measuring component of said another one measurement unit and a vertical angle of the target detected by the vertical encoder of said another one measurement unit when the target is measured by said another one measuring unit and based on said offset amounts, the one of said arithmetic control components is adapted to correct and coordinate-convert a measurement value measured in each of said measuring units. a horizontal angle encoder (9, 43, 74) adapted to detect horizontal angles, a vertical angle encoder (14, 47, 68) adapted to detect vertical angles, and an arithmetic control component (17, 49, 84), wherein said plurality of measuring units are constituted to be attachable and detachable with respect to said leveling unit respectively, each of said measuring units is selectively mounted on said leveling unit, and said plurality of measuring units are adapted to measure said target installed at a same reference position respectively, wherein, based on a measurement result of said target, one of said arithmetic control components is adapted to measure an azimuth angle offset amount which is a difference between a horizontal angle detected by the horizontal angle encoder of one measuring unit of said plurality of measuring units, when the target is measured by said one measuring unit and a horizontal angle detected by the horizontal angle encoder of another one measuring unit of said plurality of measuring units when the target is measured by said another one measuring unit and a machine height offset amount which is a difference between a height of the target calculated from a distance measurement of the target measured by the distance measuring component of said one measurement unit and a vertical angle of the target detected by the vertical encoder of said one measurement unit when the target is measured by said one measurement unit and the height of the target calculated from a distance measurement of the target measured by the distance measuring component of said another one measurement unit and a vertical angle of the target detected by the vertical encoder of said another one measurement unit when the target is measured by said another one measuring unit and based on said offset amounts, the one of said arithmetic control components is adapted to correct and coordinate-convert a measurement value measured in each of said measuring units.