A biological signal with small amplitude is detected with greater sensitivity than before. A mechanical amplification device provided with a three-dimensional knitted material 10 and plate-shaped foam bodies 21 and 22 laminated in the periphery of the three-dimensional knitted material, preferably a mechanical amplification device provided with a film 16 disposed between the three-dimensional knitted material 10 and the plate-shaped foam bodies 21 and 22 is provided, and a vibration sensor 30 is attached to this mechanical amplification device. Micro vibration on the body surface caused by a human biological signal such as heart rate, respiration, atrial and aortic vibrations and the like is propagated to the plate-shaped foam bodies 21 and 22, the film 16, and the three-dimensional knitted material 10, and membrane vibration is generated in the plate-shaped foam bodies 21 and 22 and the film 16, while string vibration of a fiber is generated in the three-dimensional knitted material 10. As a result, the biological signal such as heart rate, respiration, atrial and aortic vibrations and the like can be accurately transmitted.
