A peristaltic pump includes a removable carrier against which a flexible tube is pressed by rollers. The carrier includes an intermediate deformable section having an internal cylindrical surface whose axis coincides with the main axis of rotation of the rollers and lateral rigid arms arranged on both sides of the intermediate section. The free ends of the lateral arms include guides. The pump case is provided with paths on which the guides are slidable. The path directions are predefined in order to constrain the displacement of the free ends of the lateral arms and to deform the intermediate section in such a way that the radius of the internal face is modified keeping the axis thereof coinciding with the main axis, thereby making it possible to use a tube having variable characteristics.