To correct posture (direction of travelling) of a robot main body at that time, by utilizing a level difference detected by a level difference detection sensor.

When a level difference detection means detects a level difference during cleaning (determined Yes at S2), the self-propelled cleaning robot stops once (S3), the robot main body rotates to the left (S4), continues to rotate until the level difference detection means detects a boundary portion of the level difference (determined Yes at S5), and then stops (S6). Next, from that position, the robot main body rotates to the right (S7), and an angle detection means starts to measure a rotation angle simultaneously with the rotation starting (S8). Then, the robot main body continues to rotate to the right until the level difference detection means detects the boundary portion of the level difference again (determined Yes at S9) and stops (S10). Next, the robot main body rotates to the left only by the half angle of a detected angle at that time and stops (S11). Thereby, the posture is corrected so that the travelling direction may become orthogonal to the boundary portion of the level difference.