To provide an oil pump device of an internal combustion engine furnished with at least two of first and second oil force feeding parts independent from each other capable of improving efficiency of an oil pump so as not to make the oil pump work more than the necessary lowest limit discharge by changing oil force-fed from an oil pump unit by feed-back hydraulic pressure by a change-over valve.

This oil pump device of the internal combustion engine is constituted by providing a first oil passage to connect the first oil force feeding part and a main oil passage to each other, providing a regulator valve free to lubricate oil to each part of a power train only at under set pressure on the main oil passage, providing the change-over valve free to force feed the oil to the main oil passage only under the set pressure to the second oil passage, providing a third oil passage to connect the regulator valve and each part of the power train to each other and providing a feed-back passage to connect this third oil passage and the change-over valve.