To provide an extruder with a gear pump which is excellent in responsiveness during revolution, which is reduced in cost and which can cool the material.

In the extruder with the gear pump, the gear pump includes a drive pinion arranged concentrically with a screw and fixed at the top end of the screw, one or more follower pinions which engage with the drive pinion so as to be driven, and a gear case which is secured to a barrel to receive these pinions. The gear case comprises side plates and a casing. Rubber suction holes are provided at positions of the suction-side side plate respectively corresponding to the sides of engagement portions between the drive pinion and the follower pinions where the teeth of the respective pinions start to separate from each other. Rubber discharge holes are provided at positions of the discharge-side side plate respectively corresponding to the sides of the engagement portions between the drive pinion and the follower pinions where the teeth of the respective pinions come closer to each other. Axial communication between the rubber suction holes and the rubber discharge holes is intercepted by the pinions.