A robot arm is provided at a forward end thereof with a rotation shaft member rotatable about a rotation axis thereof, in which a hollow portion is formed along the rotation axis. A laying device for laying a line element includes a relaying means for relaying an arm side section of the line element, extending through the hollow portion out of a lead-out opening formed on a side of the rotation shaft member, to a tool side section of the line element extending from the tool. A direction in which the relaying means connects the line element is substantially parallel to a tool mount surface and forms an angle other than 0.degree. with regard to a radial direction perpendicular to the rotation axis.