<p>A biosensor includes a diaphragm (2) having a through hole (1) and also includes a frame (3) supporting the diaphragm (2) and having a cavity (4). Cut grooves (6) are formed in the frame (3) so as to extend from its end surface (5), and the surfaces of the cut grooves (6) are made to be hydrophilic. The construction suppresses the occurrence of bubbles near the through hole (1) and efficiently removes remaining bubbles. As a result, bubbles adhering to the vicinity of the through hole (1) are removed to improve reliability of measurements by the sensor.</p>
