1. An automatic mower that automatically performs an operation in an operation area, the mower comprising: an image analysis unit configured to extract a marker included in an image captured by a camera provided on the mower, wherein if a situation, in which the marker that was extracted from one image captured by the camera cannot be extracted by the image analysis unit from another image captured by the camera, has occurred during a movement of the mower in a constant direction: the image analysis unit determines whether the marker extracted before an occurrence of the situation and the marker extracted after an elimination of the situation are the same marker, using a result obtained by comparing a shape feature of a landscape near the marker included in the image captured by the camera before the occurrence of the situation with a shape feature of a landscape near the marker included in the image captured by the camera after the elimination of the situation.