The invention relates to a robot device for checking foreign matters on transmission lines. The robot device comprises a travelling mechanism, a balancing mechanism and a camera shooting mechanism which moves along the travelling mechanism and checks foreign matters on a transmission line, wherein the travelling mechanism comprises a pair of pulleys which travel on the transmission line in a rolling manner and are arranged in tandem, the balancing mechanism comprises first balancing bars which are used for installing the pulleys respectively and are arranged in a mode of being coaxial with thecorresponding pulleys, and each first balancing bar is provided with a counter weight which moves along the axial direction of the first balancing bar and is used for balancing the pulley. The pulleys can move along the transmission line, the transmission line is shot and scanned through the carried camera shooting mechanism, a corresponding control center can acquire whether the transmission line carries a foreign matter or not and information such as the specific position of the foreign matter in real time, thereby being convenient for the power maintenance personnel to timely discover andeliminate the foreign matter. The robot device can avoid long-time power interruption due to manual foreign matter checking and eliminating for the transmission line, and greatly improves the operation efficiency. The robot device not only can handle dangerous situations in time, but also can reduce personal safety risks.