A biosensor having a satisfactory wearing comfort is provided, taking the compressive elastic modulus, the thickness and the planar area of the component into account. The biosensor includes a substrate having a rigidity K of 3.0 N·mm2 or less expressed by following formula (1), and a component provided on a first main surface of the substrate, the component having a rigidity that satisfies following formula (2) and is equal to or greater than a predetermined value,

K=ET3/12  (1)

K≤6.34×1014×S−10.6  (2)

where E and T in formula (1) denote a compressive elastic modulus at 23° C. expressed in megapascals (MPa), and a thickness expressed in millimeters (mm), respectively. In formula (2), K denotes the rigidity expressed by formula (1) in newton millimeters squared (N·mm2), and S denotes a planar area expressed in square centimeters (cm2).