To obtain a small-sized inexpensive pump device which has a rotor provided with a hole for lockingly supporting a driving shaft and arranged inside a pump casing, which casing is composed of a cup-like first casing part and a second casing part having a through-hole.

A second casing 17 has an aligning device 21 which is used for previously aligned to a driving shaft 11 in assembling. In addition, a pump device 1 has a pump 3 provided with a rotor 7 having a hole 9, and a driving device 43 provided with the driving shaft 11 for driving a pump 3. In such a pump device 1, the driving shaft 11 is lockingly engaged with the hole 9 of the rotor 7.