A blood pump (1) comprises a pump casing (2) having a blood flow inlet (21) and a blood flow outlet (22), and an impeller (3) arranged in said pump casing (2) so as to be rotatable about an axis of rotation, wherein the impeller (3) has blades (31) sized and shaped for conveying blood from the blood flow inlet (21) to the blood flow outlet (22). The blood pump (1) further comprises a drive unit (4) for rotating the impeller (3), the drive unit (4) comprising a plurality of posts (40) arranged about the axis of rotation (10), wherein each of the posts (40) includes a shaft portion (41) and a head portion (42). Coil windings (47) around the posts are sequentially controllable so as to create a rotating magnetic field. The drive unit (4) further comprises a back plate (50) which engages ends (44) of the shaft portions (41) of the posts (40) opposite the head portions (42).
