To provide a compact gear pump device having a structure not applying bending stress on a drive shaft of a gear pump for rubber extrusion.

This gear pump device includes a gear pump 2, a drive device of the gear pump 2, sprockets fixed on a drive shaft of the gear pump 2 and an output shaft of the drive device respectively, and a chain 26 wrapped around the sprockets. The gear pump device includes a shaft support member 30 provided with bearings 31, 32 near both ends. The drive shaft 25 of the gear pump 2 and an output shaft 22 of the reduction gear 21 are supported by the bearings 31, 32 of the shaft support members 30.