A surveying instrument which comprises a rotation unit 7 adapted to direct a distance measuring optical axis to an object to be measured and the rotary drive unit 5 rotates the rotation unit, comprising a rotary motor for rotating an output shaft 6 and a clutch unit for connecting or disconnecting the rotary motor and the output shaft, wherein the rotary motor and the clutch unit are arranged in a series along the output shaft, and the output shaft is fixed to the rotation unit.