PROBLEM TO BE SOLVED: To provide a method capable of quickly and highly accurately measuring the change in pressure applied to a signal transmission and reception surface of a diagnostic tool when measuring structure information on the interior of an organism by using the diagnostic tool such as an ultrasonic probe.SOLUTION: A pressure vibration body 1 including a piezoelectric vibrator and a contact piece having a swollen part on one surface and the swollen part of which is arranged in contact with the surface of the piezoelectric vibrator, the swollen part being formed of an organic polymeric elastic material having a physical property indicating change in a contact area between the swollen part and the piezoelectric vibrator in accordance with the pressure change of the organism when an organism contact surface 22 is placed in a state of being in contact with the body surface of the organism, is arranged on the surface of the organism to be measured together with the signal transmission and reception surface of a diagnostic tool in a state of being in contact with the organism contact surface of the contact piece. The change in impedance of the piezoelectric vibrator of the pressure vibration body 1 is calculated and the change in the impedance is converted into the change in pressure.
