hereinunder described while the needle part 15c of the valve body 15 closes the communication hole 19 if the discharge pressure is decreased to the value which conforms to the following formula 2 the valve body 15 is shifted to the direction of opening the communication hole 19 and the intermediate pressure is maintained at a pressure lower than a normal pressure fig4 shows another embodiment of the present invention and this embodiment is different from the one shown in fig2 at the point that the position where a communication hole 19a is opened is provided in an airthight chamber 11b of a compressor part 2 in which a pressure is lower than the intermediate pressure also in this embodiment operation principle is basically the same as the one shown in fig2 and if ps is substituted by ps 39 a pressure in the airtight chamber llb in the formulae 1 and 2 the same performance and effect as described by fig2 can be realized still another embodiment of a scroll compressor of the present invention is hereinunder described with reference to fig5 through fig7 this embodiment is the same as fig1 except for a valve 113 and a part of a compressor part 200 in fig5 the scroll compressor is provided with a valve generally designated by the reference numeral 113 at the stationary scroll 107 the valve 113 is constituted by a.