To provide a fetal heart beat microphone reduced in influence of noise.

A fetal heart beat microphone 1 is brought into contact with the body of a pregnant mother to listen fetal heart beat generating in vivo. A microphone element 2 outputs electric signals corresponding to vibration detected from a contact surface 8 with the body of the pregnant mother. An inner case 3 stores the microphone element 2. An outer case 6 is set so as to cover the outside surface of the inner case 3. The inner case 3 and the outer case 3 are connected via two support members 5-1 and 5-2.