To provide a method for lining the inside of a pipe existing inside a building, which forms a thicker coating film on the inner surface of a first elbow at the side starting feeding a coating.

After the coating film of a required thickness is formed over all the length of the pipe by dividing the pipe into coating sections of branched pipes, each of which ranges from a base end part side fitted with a meter of the existing pipe to a tip end part side, by feeding a coating from the end part elbow of the branched pipe in each coating section, and by blowing and expanding the coating toward the base end part side, the end part elbow 2a of each branched pipe is connected to a coating feed part 6 having a socket-shaped coating housing part 10 and to an air feed means 9 for heated fluids, the resistor of a top member 11 is arranged in the coating housing part 10, a required quantity of coating is housed therein, and coating is performed by spraying a coating of the coating housing part 11 through the air feed means 9 toward the end part elbow 2a. The thicker coating film is formed on the inside surface of the end part elbow 2a of the starting end part where a coating is fed and coating is performed, thereby producing a coating film of a well balanced thickness throughout.