<p>Provided is a small slender device capable of measuring the internal pressure of fluid flowing through a lumen of a living body. The measurement device (10) is equipped with: a guide wire (11), the tip of which can be inserted into a lumen; a hot wire flow meter (23) provided on the tip of the guide wire (11); a cantilever (32) provided towards the tip of the guide wire (11); a piezoelectric element (37) for measuring the displacement of the cantilever (32); and a contact sensor (31) provided on the tip of the cantilever (32). The internal pressure in the lumen can be calculated on the basis of the flow velocity obtained by the hot wire flow meter (23). The internal diameter of the lumen can be measured on the basis of the displacement of the cantilever (32).</p>
