To provide an electric compressor for combustible gas and a combustible gas supply system, suitable for the combustible gas.

Gaseous hydrogen flows from an intake port 11 into a housing 13, and then flows into a compressor 15 while pushing and bringing residual gas around an electric driving machine 14 to the compressor 15. Pressure around the electric driving machine 14 in the housing 13 is equal to pressure in the intake port 11, and is lower than pressure of the gaseous hydrogen compressed by the compressor 15. Therefore, wall thickness of the housing 13 can be thin. Since fresh gaseous hydrogen is always supplied, concentration of the hydrogen becomes higher than explosion limit concentration to restrain combustion without concentration management. Further, flowing exotic component gas such as oxygen is prevented from accumulating around the electric driving machine 14 in the housing 13 which restrains the combustion.