[Object] To provide a pressure detection device which can suppress sluggishness of a circulating liquid, decrease the manufacturing cost and the capacity of a liquid flow route, prevent an error due to a difference between separate peristaltically-actuated tubes or displacement detecting means, and detect pressure in the liquid flow route with higher accuracy.[Solution] A pressure detection device of a liquid flow route includes: displacement detecting means 18 that detects displacement of a peristaltically-actuated tube 1a in the radial direction pressure calculating means 20 that is able to calculate blood removal pressure based on the displacement of the peristaltically-actuated tube closed flow route forming means that is able to form a closed flow route which includes a portion at which the displacement detecting means 18 is disposed pressure changing means that is able to arbitrarily change the pressure in the closed flow route pressure detection means that is able to detect pressure change in the closed flow route and calibration curve acquiring means 26 that is able to produce and acquire a calibration curve with which the displacement detecting means 18 and the pressure calculating means 20 are calibrated by a relationship between the pressure change detected by the pressure detection means and a detection value of the displacement detecting means 18.
