PURPOSE: To easily form a photosensitive layer consisting of different multiple layers by housing one heating source provided with a control system and plural vapor deposition raw material vessels into one evaporating source and varying the heating up rates by heating with the vessels.

CONSTITUTION: Two pieces of the evaporating raw material vessels 3 and one piece of another evaporating raw material vessel 4 are disposed in the evaporating source 2 having a slit-shaped aperture 1 and the vessel 4 is formed larger in size, wall thickness and heat capacity. A heater 5 is disposed to the vessels 3 so as to be more liable to receive heat than the vessel 4. The raw material 6 for a 1st layer is charged into the vessels 3 and the raw material 7 for a 2nd layer into the vessel 4 in the above- mentioned constitution. The raw materials are heated by the heater 5. Since the vessels 3 are liable to receive heat, the temp. thereof rises earlier and the raw material 6 for the 1st layer evaporates first. The vapor thereof emits from the aperture 1 to form the 1st layer on a substrate. On the other hand, the temp. of the vessel 4 rises slowly and the raw material 7 for the 2nd layer evaporates with a delay to form the 2nd layer on the substrate. The photosensitive layer having the two-layered structure is thus formed.