<p>A sheet member (3) holds pressure sensing sensors (21-25) and wiring (4) which is led out of the pressure sensing sensors. The sheet member (3) has a base section (31) and branch sections (32, 33). The base section (31) holds the three pressure sensing sensors (21-23) arranged on an imaginary straight line (C). The branch sections (32, 33) hold the pressure sensing sensors (24, 25). The branch sections (32, 33) are branched and extended continuously from the intermediate position between the pressure sensing sensor (21) and the pressure sensing sensor (22) which are held on the base section (31).</p>
