To provide a body pressure fluctuation detector attachable to an optional part of a living body and capable of measuring voltage signals on the pulse and pulse waves without restricting the living body that acts freely, and transmitting the voltage signals to the outside.

A sensor/circuit part for acquiring the voltage signals on the pulse and pulse waves of a tail 7 of a mouse detects the voltage signals from the pressure fluctuation of a body surface of the tail 7 of the mouse by a piezoelectric sensor 10 formed by alternately laminating sheet-like piezoelectric bodies 14, 15, sheet-like external electrodes 12, 13 and internal electrodes 16. The sensor/circuit part includes a fixing member 11 pressing and fixing the piezoelectric bodies 14, 15, the external electrodes 12, 13 and the internal electrodes 16 to the tail 7 of the mouse, and a first transmitting/receiving circuit part for transmitting the voltage signals to the outside.