PURPOSE: To provide an electric motor-operated compression device which is simple, low-cost, and easy to maintain and constituted to eliminate a check valve apt to fail in operation.

CONSTITUTION: In an electric motor driven-compression device 500, a gas substance 120 to be pressurized is pressurized by a compression mechanism 100 driven by an electric motor 200 to produce a pressure gas substance 130, which is caused to flow to a load line 300 through check valves 53 and 54. In a case the check valves 53 and 54 are not provided, the compression mechanism 100 is reversed only in a way that a power source 220 for an electric motor 200 is disconnected and the compression mechanism 100 is brought into a stop. At least the check valve 53 on the suction port 51 side of the check valves 53 and 54 can be brought into a rest in a way that the electric motor 100 is forced into an electric brake state until a pressure difference between the suction port 51 side and the delivery port 52 side of the compression mechanism 100 is reduced to a value below a pressure difference at which the compression mechanism 100 can not be reversed. Two-phase application brake wherein only two phases of three phases are applied for brake or direct current brake wherein direct current generated by rectifying an alternating current is applied for brake is used as electric brake.