The present invention relates to an obstacle detection device, adapted for an autonomous mobile system, which comprises: a conducting wire, a first unit and a second unit. The first unit further comprises a first conducting part, electrically connected to an end of the conducting wire; and the second unit further comprises a second conducting part, electrically connected to another end of the conducting wire other than that connecting to the first conducting part. As an abnormality, such as the autonomous mobile system comes into contact with an obstacle, or misses a step, is happening and detected by the obstacle detection device, a reactive force will be generated to force the two conducting parts to contact with each other so as to enable an electrical conduction for issuing an electrical signal to the control unit of the autonomous mobile system and thus enabling the autonomous mobile system to react with respect to the abnormality.