To provide a mobile robot cleaner capable of being operated with a plurality of modes for effective coverage processing.

The mobile robot cleaner includes a driving mechanism for making a circular robot body advance/rotate, a collision sensor for detecting an obstacle having contact with the robot body, a tracking sensor for detecting an obstacle of the ruling side of the robot body, a cleaning head for collecting dust from a floor, and a controller for controlling the driving mechanism based on outputs from the collision sensor and the tracking sensor. The controller can switch between a direct line mode and a bounce mode. The controller controls the robot body with the direct line mode to advance along a direct line until the collision sensor detects an obstacle, and with a bounce mode to rotate to leave from the obstacle when the collision sensor detects the obstacle, and then with the direct line mode to directly advance along a changed direction.