A drive power distribution device includes a hydraulic pressure sealing-type hydraulic pressure control device for making an operation noise of an on-off valve such as a solenoid valve less recognizable to occupants of a vehicle. By closing the on-off valve and driving the oil pump, a hydraulic pressure detected using a hydraulic pressure detection means reaches a target hydraulic pressure, and fastening power of a hydraulic clutch is maintained at an oil pressure of hydraulic fluid sealed in an oil passage until the on-off valve is opened. The drive power distribution device closes the solenoid valve when the hydraulic pressure is detected to be equal to or less than a predetermined threshold hydraulic pressure and equal to or less than a predetermined threshold vehicle speed. This can prevent synchronization between an accelerator operation by a driver and a closing operation of the solenoid valve.