PROBLEM TO BE SOLVED: To provide a small slender device capable of measuring the internal pressure of a fluid flowing through a lumen of a living body.SOLUTION: A measurement device 10 comprises: a guide wire 11, the distal end of which is insertable into a lumen； a hot wire flowmeter 23 mounted on the distal end of the guide wire 11； a cantilever 32 provided toward the distal end of the guide wire 11； a piezoelectric element 37 for measuring the displacement of the cantilever 32； and a contact sensor 31 mounted on the distal end 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 flowmeter 23. The internal diameter of the lumen can be measured on the basis of the displacement of the cantilever 32.
