To provide a method for preventing the clogging of a flowing passage with which in the case of heating molten iron by using a groove type induction heating apparatus having the groove type flowing passage, and even in the case of sticking foreign matters, such as slag in a furnace, enclosed in the molten iron, oxide generated in the furnace, to the flowing passage, the stuck foreign matters can effectively be removed and the reducing and the clogging of the flowing passage caused by the sticking of the foreign matters can be prevented.

When the molten iron stored in a molten iron storing furnace provided with the induction heating apparatus by using the induction heating apparatus 6 having the groove type flowing passage 10 is subjected to induction heating, a steel ball 12 having smaller diameter than the inner diameter of the flowing passage is passed through the flowing passage by carrying in the flowing of the molten iron to remove the foreign matters stuck to the inner wall of the flowing passage by passing through the steel ball.