PURPOSE: To secure such a three-throw gear pump that is high in cavitation limit revolving speed and possible for high-speed operation, by setting up an inscribed gear in the inside of either or two circumscribed gears in mesh with each other.

CONSTITUTION: A first driven gear 7 and a second driven gear 9 both are engaged with each other as being set down to circumscribed gears. On other hand, a drive gear 5 is engaged with the internal gear 11 concentrically formed in the driven gear 7 as being set down as an inscribed gear. With this constitution, since an internal gear pump is additionally formed inside the first driven gear 7 or one side gear of an external gear pump, such a three-throw gear pump that is simple in each form of a pump body 1 and a pump cover 3 is securable and simultaneously a suction port and a discharge port are put together in one lot. In addition, since a suction angle can be made larger enough, the extent of cavitation limit revolving speed is raised up, thus it comes to make high-speed operation performable in consequence.