A pair of drive wheels are disposed in a middle region of a travel body section in a body length direction and are separated from each other in a body width direction. A first drive source is disposed on a first side in the body length direction relative to a width direction reference line and a first side in a body width direction relative to a length direction reference line in top-down view. A second drive source is disposed on a second side in the body length direction relative to the width direction reference line and a second side in the body width direction relative to the length direction reference line in top-down view.