A stick-on biosensor capable of acquiring satisfactory biological information is provided. The stick-on biosensor includes a pressure-sensitive adhesive layer and an electrode part, said pressure-sensitive adhesive layer having a stick-on surface to be attached to a subject; a base material layer provided on the side opposite the stick-on surface of the pressure-sensitive adhesive layer; and an electronic device provided on the base material layer and configured to process a biological signal acquired through the electrode part. A structure, which includes the pressure-sensitive adhesive layer, the electrode part, and the base material layer, has a flexural rigidity of 0.010 [MPa·mm3/mm] or higher, and an adhesive strength of the electrode part to adhere to the subject is greater than 0.6 [N/cm2] and less than or equal to 5.0 [N/cm2].