When the distribution of the pressure applied to a mat is measured and a plurality of detection units is established in the air mat and the sensor for measuring the pressure applied to the air mat is needed to be provided for each detection unit. The mat for pressure measurement 2 is arranged the first medium accommodation object 21b ON the right side and the second medium accommodation object 22b ON the left side. The first connecting pipeline 21a is connected to the first medium accommodation object 21b and the second connecting pipeline 22a is connected to the second medium accommodation object 22b and respectively. Since the internal diameter K4 of the second connectingpipeline 22a is set smaller than the internal diameter K2 of the first connecting pipeline 21a and the pipeline length of the second connecting pipeline 22a is set longer than that of the first connecting pipeline 21a in the mat for pressure measurement 2, the pressure loss coefficient of the second connecting pipeline 22a has a greater value than that of the first connecting pipeline 21a.
