detailed description of redundant portions will be omitted 1 after the beltlike substrate 103 is set the pressure reducing operation is first started specifically the roughing pump 106 is actuated to decrease the pressure inside the outer chamber 101 down to a substantial vacuum of about 0 1 mtorr next evacuation is switched to the main evacuation pump 104 to raise the vacuum degree to a substantial vacuum of approximately 10 4 torr 2 next carried out is heating and baking of the beltlike substrate 103 and the walls of the deposition chamber first the gas of he h 2 or the like is guided through the guide inlet pipe 108 into the deposition chamber 102 adjusted at an appropriate flow rate by a gas flow rate controller not shown the gas thus introduced into the deposition chamber 102 flows into the outer chamber through the holes of punching metal louver expanded metal or the like forming the deposition chamber wall 131 and the gas is then evacuated by the vacuum pump 104 the pressure inside the deposition chamber can be adjusted to a desired pressure by controlling the valve travel of the valve 107 as observing the pressure meter 115 the pressure is preferably one near the pressure for carrying out microwave film deposition specifically 1 to 30 mtorr approximately the beltlike substrate is heated by the lamp heater 109 up to the temperature normally considered to be preferable for.