Biological sound detection device

A biological sound detection device capable of detecting a desired biological sound signal while suppressing a level of noise signal is provided. The biological sound detection device (100) comprises a sound collecting space (3) for the biological sound, a membrane (8) covering an opening thereof, a microphone (2) located in a back space, which is communicated with the sound collecting space (3), and a signal processing part (7) for signal processing of a biological sound signal. The microphone (2) is composed of a capacitance type microphone and positioned so that a pressure applied to the membrane (8) is applied to a vibrating membrane through a backplate and a displacement of the vibrating membrane occurred from the pressure is started from the displacement to the direction away from the backplate. A volume of a space between the membrane (8) and the vibrating membrane is set so that the vibrating membrane does not contact with the backplate when the vibrating membrane is displaced to a direction close to