PURPOSE: To solve the problem of positional deviation of each nozzle caused by recombination of nozzles and obtain a CVD device in which the release direction of a gas performed by a replaced nozzle does not change in comparison with that performed by the previous nozzle by forming a plurality of gas releasing ports of a ring-shaped nozzle so that all of above ports have the same diameter and further, they attain the size in such an extent that their conductance can be disregarded.

CONSTITUTION: Each nozzle 19 in which a plurality of gas releasing ports 17 having the same diameter in the circumferential direction are formed is formed as a ring that is divided into two parts in such a way that, being formed into a square shape, each flowing path cross section has a large area. The ring is formed inside of a deposition prevention cylinder 21 and each mounting face to a ledge 21a is finished to a smooth surface. The cross sectional area of the circumferential flowing path of the ring-shaped nozzle 19 is formed to attain the size in such a manner that the conductance of each gas releasing port 17 can be disregarded substantially as compared to the conductance of the flowing path. A CVD device is thus obtained so that a change in flowing-in cross sectional area caused by positional deviation to a gas introduction tube path in the case where the nozzle is recombined to the other nozzle does not take place.