A biosensor includes a pressure-sensitive adhesive layer for attaching to a surface of a living body, a substrate layer disposed on an upper face of the pressure-sensitive adhesive layer and having a stretching property, a probe disposed on the lower face of the pressure-sensitive adhesive layer, and an electronic component mounted on the substrate layer so as to be connected to the probe, wherein a total thickness of the pressure-sensitive adhesive layer and the substrate layer is 1 µm or more and less than 100 µm.
