[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.