Abstract: Water mains, water pipes of apartment houses or water pipes of factories with an inner diameter that varies in size in order to accommodate the sections where branch pipes are installed can be lined by this method. Firstly, mixed fluid formed by mixing paint and air is blown into a pipe line to be lined wherein the pipe line is comprised of a number of sections each having a different diameter. The mixed fluid is blown into the end of the section with the smallest diameter. A flow volume of mixture fluid that passes through the pipe with the smallest diameter is regulated for the optimum value for the size of the pipe with the smallest of diameter. Next, additional compressed air to be used for fluid volume regulation is blown into the sections of the pipe where an inner diameter varies so that the flow volume of mixture fluid that passes through the sections where an inner diameter of the pipe line varies is regulated for the optimum flow volume for the size of the pipe.