In an autonomously navigating vehicle including a sensor (contact-lift sensor) configured to produce an output proportional to displacement between a chassis and the cover and the control unit configured to receive output of the sensor, wherein the control unit is configured to determine whether change of the sensor output per prescribed time period is equal to or greater than the threshold value, count up time period during which change has been determined to be equal to or greater than the threshold value, and compare time period counted up by the time integration unit with prescribed time periods (first prescribed time period and second prescribed time period) and discriminate whether the vehicle has contacted an obstacle or whether the cover has been lifted from the chassis based on the result of the comparison with the prescribed time periods.
