[Object] To provide a pressure detection device which can suppress stagnation of a circulating liquid and decrease the manufacturing cost and the capacity (priming volume) of a liquid flow route. [Solution] A pressure detection device of a liquid flow route is provided which detects a pressure of an arterial blood circuit 1 consisting of a flexible tube, a portion of which is connected to a peristaltically-actuated tube 1a that can cause an internal liquid to flow by being compressed in a radial direction and being peristaltically actuated in a longitudinal direction in a roller 10 of a blood pump 4, and which enables a predetermined liquid to be circulated. The pressure detection device includes a load sensor 18 that detects radial displacement of the peristaltically-actuated tube 1a.
