To provide an unmanned rotorcraft and a method for measuring a distance to a circumjacent objet around the rotorcraft, enabling it to prevent its airframe from colliding with a circumjacent object when flying and prevent its airframe from falling down when landing, while suppressing an increase in airframe cost. This is solved by an unmanned rotorcraft including a distance sensor to measure a distance between its airframe and a circumjacent object around it, the distance sensor and its detection direction being fixed to the airframe, and a method for measuring a distance to a circumjacent objet around the rotorcraft, adapted to watch or watch out for a circumjacent object around the airframe by turning the airframe automatically in a yaw direction under predefined conditions or to measure a difference of elevation at landing points of all legs of the airframe.