A laying method for laying communication cables (16) is provided which allows to lay optical fiber cables (20) in an underground pipeline such as a sewage pipe neither placing direct tension nor allowing slack on them, and for a main pipe in which a plurality of optical fiber cables (20) are to be laid, the method also allows to lay optical fiber cables (20) in the upper space of inside the pipeline and to obviate the need of an expensive robot for the laying operation. In the proposed laying method, a high-strength low-elongation tension member is disposed to be slidable in the lengthwise direction along each optical fiber cable (20, 21, 22), and the tension members (25, 26, 27) are drawn into the underground pipeline (1) to tension the trunk tension member (25) thereby stretching the trunk tension member (25) substantially straight in the underground pipeline (1), and thus the optical fiber cables (20, 21, 22) are laid in the upper space of inside the underground pipeline (1). Also the branch tension member (26, 27) is tensioned in the branch pipe (4, 5) to lay the optical fiber cables (21, 22) in the branch pipe without allowing slack.