A peristaltic pump for an apparatus for extracorporeal blood treatment, especially for a dialysis machine, for delivering fluid in the apparatus is disclosed. The peristaltic pump includes a rotor driven to rotate about a rotor axis and a pump casing surrounding the rotor at least in part and including a supporting surface being configured to be curved around the rotor axis, wherein an elastically deformable fluid line is adapted to be positioned between the rotor and the supporting surface and is deformed between the rotor and the supporting surface while forming a cross-sectional constriction for fluid delivery by rotation of the rotor, the pump casing having a modular design and including a supporting surface module forming the supporting surface and a casing module adapted to be coupled to the former and surrounding the rotor at least in part.
