Disclosed herein is a system for automatically cleaning boiler pipes, which includes a pipe-cleaning tank provided on one side of a casing to store a cleaning solution therein and a tank supply valve provided in the pipe-cleaning tank, so as to allow the cleaning solution stored in the pipe-cleaning tank to automatically flow into a heat exchanger and various pipes inside the casing by means of only a simple operation of manipulating the tank supply valve, thereby making it easy to eliminate scale that has accumulated in the heat exchanger and the pipes.