To provide a foreign material removal device and its method which can reliably remove the foreign material clogging a pipe, even in a narrow piping.

A cutting tool 12 is secured at the tip part of a supporting arm 11, which is freely bendable, a protection cover 13 is secured at the outer circumference part of the cutting tool 12, and a bearing 14 for centering is fit at the outer circumference part of the protection cover 13. A power drill 15 is connected to the base end part of the supporting arm 11 to constitute the unit. A protection tube 16 is inserted into a heat transfer pipe P, and the cutting tool 12 is inserted into the protection tube 16. The cutting tool 12 is rotated by the power drill 15 through the supporting arm 11, and the foreign material is cut and removed by pressing the cutting tool 12 onto the foreign material E.