It is an object of the present invention to provide an electric compressor capable of enhancing the mountability with respect to a vehicle without increasing the compressor in size when the electric compressor and a motor-driving circuit which drives a motor of the electric compressor are integrally formed together. A suction chamber 61 which is in communication with a fixed panel suction port 16 provided in a fixed scroll 11 from a suction port 8 provided in a sub-casing 102, and a discharge chamber 62 which is in communication with a communication passage 63 from a fixed panel discharge port 31 provided in the fixed scroll 11 are disposed on the same plane in a radial direction of a compressor, and the motor-driving circuit 101 is disposed in an axial direction of the compressor so that an IPM 105 which is a heat generating part of the circuit substrate 103 can be brought into tight contact with the suction chamber 61.