<p>A biosensor includes a diaphragm (2) having a through hole, a frame (3) supporting the diaphragm (2) and having a cavity (4), and pillars (6) formed on that surface of the diaphragm (2) which is on the inner wall surface (6a) side of the frame (3). The construction suppresses the occurrence of bubbles near the through hole and remaining bubbles are easily removed. This improves reliability of measurements by the biosensor (20).</p>
