An object is to provide an electric supercharging device that has a high degree of freedom in layout and can suppress the generation of heat from an electric motor. The electric supercharging device 1 includes an electric motor 2, a compressor 3 that supercharges intake air for a vehicle engine, a hydraulic accelerator 10 that accelerates the rotation of the electric motor 2 and transmits the rotation to the compressor 3, and rotation speed adjustment means 4 that controls the rotation speed of the electric motor 2 and an acceleration ratio of the hydraulic accelerator 10 and adjusts the rotation speed of the compressor 3. The hydraulic accelerator 10 includes a variable displacement hydraulic pump 12 that is connected to the electric motor 2 and is driven by the electric motor 2, a variable displacement hydraulic motor 14 that is connected to the compressor 3 and is driven by hydraulic oil supplied from the hydraulic pump 12, and a hydraulic circuit 13 that is formed by the connection between the hydraulic pump 12 and the hydraulic motor 14.