the discharge space circumscribed by a plurality of cylindrical substrates are activated by plasma discharge to cause the formation of a deposited film on each of the plurality of cylindrical substrates and the remaining gas not consumed in the formation of said deposited film is exhausted outside the discharge space that is the said remaining gas is mainly exhausted through spaces established between every two cylindrical substrate and part of which is exhausted through an upper space between the upper auxiliary substrate and the upper microwave introducing means and also through a lower space between the lower auxiliary substrate and the lower microwave introducing means in this connection there occur gas flows along the generating lines for each of the cylindrical substrates in the discharge space occurrence of such gas flows in plasma atmosphere causes differences in the types and amounts of molecules radicals and ions at their upstream and downstream portions this is due to the difference in time for the film forming raw material gas to be exposed to plasma and the loss of specific active species capable of contributing to the film deposition as a result the resulting deposited film becomes ununiform in the characteristics in more detail it becomes such that has a difference in the characteristics between its central portion and its end portions the present inventors have experimentally confirmed that the above problems can be effectively eliminated according to the mw pcvd process of the present invention wherein the foregoing occurrence of undesirable gas flows which is.