PURPOSE: To provide a gas compressor allowing lubricating failure, caused by the supply shortage of lubricating oil, to be avoided even with a small quantity of lubricating oil.

CONSTITUTION: The floor face of an oil reservoir chamber 5 is formed into two-stage floor face low on the compressor body 2 side and high on the bottom face side of a casing l with step difference 18 as a boundary. The inflow side opening end 17a of a feed oil passage 17 is opened onto the lower stage 18a side of the step difference 18, in a position lower than the height of the step difference 18. The cross-sectional area of the lower stage side 18a occupies micro cross-sectional area with the inflow side opening end 17a placed therein. Accordingly, it is so constituted that a limit oil level (ho) required to prevent the lubricating failure of bearing parts 12, 13 and the like caused by the supply shortage of lubricating oil, that is, an oil level preventing the inflow side opening end 17a of the feed oil passage 17 from being exposed in high pressure refrigerant gas, is maintained only with micro lubricating oil filling a micro displacement space A of the height part of the step difference 18.