PURPOSE: To realize rapid heating at a temp. rising speed of 10°C or more/sec without accompanying the oxidation and decarburizing of a steel plate by arranging a jet nozzle, which injects high temp. heating atmospheric gas to the surface of the steel plate, to a heating zone.

CONSTITUTION: An one-directional silicon steel plate material (w) preheated to the vicinity of a recrystallization start temp. through the preheating zone 5 of a continuous annealing furnace is heated at a temp. rising speed of 10°C or more/ sec in a temp. region of 500W900°C by the blast stream from jet nozzles 8 which are provided to a heating zone 6 an inject high temp. heating atmospheric gas. The jet nozzles 8 are alternately arranged in a direction at right angles to the advance direction of the material (w) running on furnace rolls 9. Furthermore, the atomospheric gas is controlled in a steam/hydrogen partial pressure ratio in order to prevent the oxidation and decarburizing of the material (w) after heated to a high temp.