[Problem] Provided are a removable pressure sensor which can simply, instantaneously, and safely measure an intra-circuit pressure of a liquid circulating in a circuit, and an extracorporeal circulator provided with a removable pressure sensor. [Means for Resolution] A removable pressure sensor 30 includes a main body portion 31 and a pressure measurement element 40 that is disposed in the main body portion 31. The main body portion 31 has a base portion 32 which has a tube mounting recessed portion 34 such that an intermediate part of a tube 11 (12, 19) is removably fitted, the tube 11 (12, 19) is elastically deformed, and the pressure measurement element 40 measures a circuit pressure of a liquid inside the tube 11 (12, 19)； and a lid portion 33 which holds the tube 11 (12, 19) inside the tube mounting recessed portion 34 by closing the tube mounting recessed portion 34 of the base portion. The tube mounting recessed portion 34 has a rectangular cross section, and a width L of the rectangular cross section is configured to be smaller than an external dimension D of the tube.
