Abstract: The present invention provides a method capable of lining a multibranch piping with a coating material within the pot life of the coating material without leaving an area uncoated or having to apply excessive repeated coatings. Lining of a main pipe is performed by pouring the coating material into the main pipe from an end portion of the pipe, and the lining of branch pipes is effected by the feed of the coating material and air for each of the branch pipes. A completed time point of lining in each branch pipe is detected by any one of the following methods:(A) A method wherein the time required for lining a branch pipe is estimated in advance and upon lapse of the estimated time it is determined that the lining of the branch pipe was completed.