An autonomous traveler comprising: a main casing ; a driving part for enabling the main casing to travel; map generation means for generating a map indicative of information on an area; self-position estimation means for estimating a self-position; information acquisition means for acquiring external information on the main casing ; and, control means for controlling an operation of the driving part based on the map generated by the map generation means to make the main casing autonomously travel, characterized in that , the information acquisition means acquires at least one of an arrangement position of an obstacle, a shape of an obstacle, a temperature of an obstacle, material of a cleaning-object surface, a step gap of a cleaning-object surface, an amount of dust and dirt on a cleaning-object surface and a color tone of a cleaning-object surface as the information on the area of an external part of the main casing , wherein when the information on the area acquired by the information acquisition means at autonomously traveling is different from the information on the area indicated in the map generated by the map generation means , the control means controls the operation of the driving part so that the main casing travels along a periphery of the position where the information is different, while making a search motion performed in which the information acquisition means acquires the information on the area, when the main casing has traveled around the position, the search motion is finished, the information acquired by the information acquisition means is reflected to the map by use of the map generation means , and the main casing is returned to autonomously traveling. a main casing ; a driving part for enabling the main casing to travel; map generation means for generating a map indicative of information on an area; self-position estimation means for estimating a self-position; information acquisition means for acquiring external information on the main casing ; and, control means for controlling an operation of the driving part based on the map generated by the map generation means to make the main casing autonomously travel, characterized in that , the information acquisition means acquires at least one of an arrangement position of an obstacle, a shape of an obstacle, a temperature of an obstacle, material of a cleaning-object surface, a step gap of a cleaning-object surface, an amount of dust and dirt on a cleaning-object surface and a color tone of a cleaning-object surface as the information on the area of an external part of the main casing , wherein when the information on the area acquired by the information acquisition means at autonomously traveling is different from the information on the area indicated in the map generated by the map generation means , the control means controls the operation of the driving part so that the main casing travels along a periphery of the position where the information is different, while making a search motion performed in which the information acquisition means acquires the information on the area, when the main casing has traveled around the position, the search motion is finished, the information acquired by the information acquisition means is reflected to the map by use of the map generation means , and the main casing is returned to autonomously traveling. <EOS>