A robot cleaner system for detecting an external recharging apparatus which is positioned in a non-detectable area by an upper camera thereof, and a docking method for docking the robot cleaner system with the external recharging apparatus. The robot cleaner system includes an external recharging apparatus with a power terminal connected to a utility power supply, a recharging apparatus recognition mark formed on the external recharging apparatus, and a robot cleaner, having a recognition mark sensor that detects the recharging apparatus recognition mark, and a rechargeable battery. The robot cleaner automatically docks to the power terminal to recharge the rechargeable battery. The recharging apparatus recognition mark is made of retroreflective material or a metal tape, and the recognition mark sensor may be a photosensor or a proximity sensor.