PURPOSE: To deposit a sufficiently thick and uniformly thick film on the surface of a specimen by a method wherein a light-transmitting window is cooled uniformly so that a film formation operation can be controlled in any position on the surface of the light-transmitting window.

CONSTITUTION: A glass substrate as a specimen 20 is housed inside a reaction container 1; a pressure inside the reaction container 1 is reduced by using an evacuation pump 5; a temperature of the specimen 20 is raised up to 250°C by using a heater 3. On the other hand, nitrogen gas which is used as a coolant is cooled by using a cooling apparatus 16 and is supplied to a space between a first light-transmitting window and a second light-transmitting window 6, 8 through a coolant supply pipe 14. While the gas is circulated to the cooling apparatus 16 through a coolant discharge pipe 15, it cools the first light-transmitting window 6 down to-10°C. The space between the first light-transmitting window 6 and the second light-transmitting window 8 is divided into a plurality of spaces by a plurality of partition walls 13 which have been installed in parallel along an incident direction (vertical direction) of light from a low-pressure mercury pump 10; the coolant supply pipe 14 and the discharge pipe 15 are connected respectively in such a way that a flow direction of the coolant becomes a reverse direction in mutually adjacent spaces.