A horizontal-type electric motor driven compressor comprises a casing, a suction chamber formed in the casing, an electric motor arranged on a suction chamber side in the casing, a compressor section driven by the motor in the casing about a horizontal axis of rotation extending in a longitudinal direction of the casing, a suction opening provided in the compressor section, and a refrigerant passage having an inlet communicating with the suction opening and communicating the suction chamber to the suction opening. The refrigerant passage is the sole refrigerant passage between the suction chamber and the suction opening. The inlet of the refrigerant passage is provided in a lowermost portion at a bottom of the casing.