The blood pump of the present invention comprises: a first casing ( 1 ), its rim forming an opening a second casing ( 2 ) having an inlet opening at the top and an outlet opening at an arbitrary position a pump base part ( 5 ) attached to the first and second casings to partition them, its one side facing and covering the rim of the first casing, and the other side facing the base rim of the second casing a drive part ( 7 ) housed inside the first casing driving a rotation shaft with a boss on the tip going roughly through the middle of the pump base part a plurality of impellers ( 11 ) extending in radial direction from the outer periphery of the boss and a pump part ( 3 ) constituted by the concurrence of the plurality of impellers and the second casing, wherein the impellers boss attachment parts are shifted forward towards the inlet opening. wherein one part is cut out in each of the plurality of impellers surfaces to form a window opening part ( 13 ). As a result, the blood pump of the present invention ensures smooth blood flow and therefore allows to effectively prevent the development of thrombi.
