To provide a hydraulic device of an internal combustion engine capable of maintaining the filtering function of a filter provided in an oil passage of an electric oil pump for a long time, and avoiding an enlargement of the electric oil pump in which an increase of pumping pressure losses attributable to clogging of the filter is assumed.

The hydraulic device comprises a mechanical oil pump 11 which is connected to and driven by an internal combustion engine 10, an electric oil pump 21 to be driven by a motor 20, an oil pan 30 to which the mechanical oil pump 11 and the electric oil pump 21 are connected, and a control unit 40 for controlling the operation of the electric oil pump 21 by controlling the motor 20. A strainer is provided in an oil passage 22 of the electric oil pump 21, and when the strainer is choked up, the control unit 40 reverses the electric oil pump 21 to perform the back-washing while the mechanical oil pump 11 is in operation.