PURPOSE: To obtain a high-quality green tea, by steaming green tea leaves uniformly by electonic energy while being transported at a fixed speed with stirring the leaves through a device.

CONSTITUTION: The device 2 is equipped slantingly with the cylinder 10 consisting of a transparent material, the cylinder 10 is supported by the bases 4, 6, and 8, and placed rotatable by the motor 16. The cylinder 10 is furnished with a screw conveyor, green tea leaves are transferred through the cylinder 10 while being stirred from the hopper 22. The device 2 is separated by the dividing wall 40, electrical radiation is irradiated from the antenna 36 of electron (electrical radiation) irradiation to each chamber, and the green tea leaves are steamed by the energy of electrical radiation. The green tea leaves irradiated by the electrical radiation for a given time and in the condition of being steamed fully are discharged from the other outlet of the cylinder 10 to the outside successively.