A pressure detection device of a liquid flow route includes displacement detecting means that detects displacement of a peristaltically-actuated tube in the radial direction pressure calculating means 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 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 that is able to produce and acquire a calibration curve with which the displacement detecting means and the pressure calculating means are calibrated by a relationship between the pressure change detected by the pressure detection means and a detection value of the displacement detecting means.
