A method of repairing a refractory lining of a vessel lined with refractory by flame gunning process, in which a patching material consisting of refractory particles and carbonaceous fuel powder is flame-gunned together with an oxygen containing gas to fuse or semi-fuse the refractory particles in a region surrounded by high-temperature flame and struck against the surface of the refractory lining to produce a deposit layer of the refractory particles, is disclosed. In this method, a patching material having a higher mixing ratio of the fuel powder or only the fuel powder is flame-gunned at an initial stage of the repairing and subsequently patching materials, in which the mixing ratio of the fuel powder is lowered stepwise, are flame-gunned in order with the progress of the repairing, during which a blow rate of the oxygen containing gas is controlled in accordance with the change of the mixing ratio of the fuel powder in the patching material.