SURVEYING INSTRUMENT

Provided is a surveying instrument equipped with an instrument height measuring unit compact in size. In a surveying instrument including an instrument height measuring unit configured to make a distance measurement by irradiating light toward a position below a vertical axis of a surveying instrument main body, and calculate an instrument height, the instrument height measuring unit includes a light transmitting unit configured to emit light, a beam splitter configured to be incident with light emitted from the light transmitting unit, split the incident light into reference light and distance-measuring light, send the reference light to a reference light path, and send the distance-measuring light to a distance-measuring light path, a first light receiving unit configured to receive the reference light, a second light receiving unit configured to receive light being the distance-measuring light that has been emitted toward a position below the vertical axis of the surveying instrument main body and returned by being reflected by a distance-measuring object, and an arithmetic unit configured to calculate the instrument height based on a difference between light reception signals generated by the first light receiving unit and the second light receiving unit. The surveying instrument has a configuration that does not need a shutter for alternatively emitting reference light and distance-measuring light and a driving unit for the shutter, and is configured with a compact size. [Selected Drawing] FIG. 1