A robot cleaner comprising: a cleaner main body equipped with a dust collecting device ; a cleaning module that is relatively movable with respect to the cleaner main body and sucks air containing dust and foreign substances; and a connection unit that is connected to the cleaner main body and the cleaning module respectively and has a variable length, wherein the connection unit forms a part of an intake flow path that guides the air sucked by the cleaning module to the dust collecting device , wherein the connection unit comprises: an outer case mounted on the cleaner main body , an inner case that is inserted into the outer case and relatively moveable with respect to the outer case , and a flexible tube which is fixed to the outer case and the inner case , respectively, and of which at least a part is provided to extend or contract according to the relative movement of the inner case , characterized in that a hole connecting with inside of the outer case is provided on an outer circumference of the outer case , and wherein the flexible tube comprises a corrugated portion including a ductile material and provided to extend or contract according to the relative movement of the inner case , and a bending portion extending from the corrugated portion and penetrating the hole . a cleaner main body equipped with a dust collecting device ; a cleaning module that is relatively movable with respect to the cleaner main body and sucks air containing dust and foreign substances; and a connection unit that is connected to the cleaner main body and the cleaning module respectively and has a variable length, wherein the connection unit forms a part of an intake flow path that guides the air sucked by the cleaning module to the dust collecting device , wherein the connection unit comprises: an outer case mounted on the cleaner main body , an inner case that is inserted into the outer case and relatively moveable with respect to the outer case , and a flexible tube which is fixed to the outer case and the inner case , respectively, and of which at least a part is provided to extend or contract according to the relative movement of the inner case , characterized in that a hole connecting with inside of the outer case is provided on an outer circumference of the outer case , and wherein the flexible tube comprises a corrugated portion including a ductile material and provided to extend or contract according to the relative movement of the inner case , and a bending portion extending from the corrugated portion and penetrating the hole . an outer case mounted on the cleaner main body , an inner case that is inserted into the outer case and relatively moveable with respect to the outer case , and a flexible tube which is fixed to the outer case and the inner case , respectively, and of which at least a part is provided to extend or contract according to the relative movement of the inner case , characterized in that a hole connecting with inside of the outer case is provided on an outer circumference of the outer case , and wherein the flexible tube comprises a corrugated portion including a ductile material and provided to extend or contract according to the relative movement of the inner case , and a bending portion extending from the corrugated portion and penetrating the hole . <EOS>