To provide a system and a method for inspecting a power transmission line using an unmanned flying body, which can automatically perform the inspection of a tree approaching the power transmission line or the like.

There are provided: an unmanned helicopter having a flight control system for performing the flight to the inspection point of the power transmission line while automatically performing the flight and an information collection system for collecting an image of the inspection point and various kinds of information including range measurement data; a control center having a flight control/information collection system for controlling the flight of the unmanned helicopter and for collecting and processing the various kinds of information from the unmanned helicopter; an approaching tree, etc. inspection means 100 for preparing a three-dimensional image from the image of the inspection point and the range measurement data collected by the information collection system of the unmanned helicopter, for processing the prepared three-dimensional image, and for inspecting whether abnormality exists in the inspection point of the power transmission line or not, on the basis of the processed three-dimensional image; and a storage device in which the various kinds of data for use in the inspection in the approaching tree, etc. inspection means 100 are stored.