PURPOSE: To restrain an increase of lubricating oil quantity (oil rising quantity) delivered together with delivery gas by providing a communicating passage to communicate the tail end of an oil discharge passage to return lubricating oil to an oil reservoir after lubricating a lubricating place of a compression mechanism with an oil suction pipe or the oil reservoir.

CONSTITUTION: This motor-driven compressor houses a scroll type compression mechanism C and an electric motor M in a closed housing 8, and these are connected to each other through a rotary shaft 5 extending horizontally. Lubricating oil in an oil reservoir 57 is sucked in by means of an oil suction pipe 56 by driving an oil pump 51 according to rotation of the rotary shaft 5, and is returned to the bottom part of the closed housing 8 by means of an oil discharge passage 62 after respective bearings 71-73 and so on are lubricated through an oil feed hole 52. In this case, the tail end of the oil discharge passage 62 is communicated with/connected to the oil suction pipe 56 through a communicating pipe 30. Lubricating oil after lubrication is introduced to the oil suction pipe 56 through the oil discharge passage 62 and the communicating pipe 30, and is flowed together with the lubricating oil being sucked up from the oil reservoir 57, and is sucked in the oil pump 51.