There is provided a surveying instrument including a monopod which is installed on a reference point, a surveying instrument main body which is provided at a known distance from a lower end of the monopod and a known angle with respect to an axis of the monopod, two auxiliary legs which extend downward from a middle portion of the monopod at a predetermined angle, and a lower image pickup module which is provided at a known position with respect to the surveying instrument main body, wherein the surveying instrument main body comprises a measuring unit, a measuring direction image pickup module, and an arithmetic control module, wherein the surveying instrument main body is supported by three points by the monopod and the auxiliary legs, and a positional change or a rotational change of the surveying instrument main body is calculated based on a change of the lower image.