A device for cardiocirculatory assistance, also named a ventricular assist device, includes a haematic pump (50) with a pump body (7) having an inner space (21) defined by a rigid structure (51) and a pair of mobile membranes (16, 17) alternately driven in opposite directions by alternately positive pressure and negative pressure gas supplied to recesses (19, 20) surrounding the two membranes by means of an external pneumatic force generating unit (1). This device achieves excellent operation results while maintaining a reduced size and reduced weight.