To repair a steam pipe easily with an inexpensive repair cost even in the case of high steam pressure and a large pipe diameter, when a steam leak is repaired without stopping circulation of a flow of steam.

In this steam leak repairing work method of a steam pipe, which repairs a steam leak from between both flanges of a flange joint part B bolt connecting the fellow flanges 1 of the steam pipe A by interposing a gasket 2 there between, an elastic strip 6 of hard quality, striding both the flanges and interposing a heat resisting seal material 5 between external peripheral surfaces of both the flanges, is wound over to almost the total periphery of both the flanges, this wound strip is fastened so as to vertically superpose the fellow end parts by a chain 7 wound to a strip external peripheral surface 6a, a part between both the flanges is air-tightly closed, and a part between both the flanges is charged with unhardened thermosetting resin 4 from a part distant from a steam leak place.