The present invention relates to a pressure detector. In a body that constitutes part of the pressure detector, a through hole is formed, which is directed upwardly from a substantially central portion of a flow passage through which a pressure fluid flows. The through hole communicates with a sensor chamber in which a pressure sensor is disposed, and a rod-shaped member is disposed displaceably in the through hole. In addition, an end of the rod-shaped member, which is exposed to the flow passage, is pressed by the pressure fluid and displaced upwardly thereby, and pressure is detected as a result of the pressure sensor being pressed by a head of the rod-shaped member.