Pressure detection device including suppressing variations

A pressure detection device comprising:

• a pressure detection unit configured to detect a pressure of a fluid;
• a flow passage unit in which a flow passage through which the fluid flows is formed;
• and
• a mounting unit configured to removably mount the flow passage unit on the pressure detection unit,
• wherein the pressure detection unit includes:
• a pressure detecting diaphragm configured to be displaced in accordance with a pressure transmitted from the flow passage unit, and
• a pressure transmitting member arranged at a center part of a first surface of the pressure detecting diaphragm, protruding toward the flow passage unit along a first axis orthogonal to the pressure detecting diaphragm, and having a top surface orthogonal to the first axis,
• wherein the flow passage unit includes:
• a flow passage diaphragm configured to be displaced in accordance with a pressure of the fluid flowing through the flow passage, and
• a cylindrical communication hole extending along a second axis orthogonal to the flow passage and communicating with the flow passage, the communication hole being closed by the flow passage diaphragm,
• wherein a displacement of the flow passage diaphragm in contact with the top surface is transmitted to the pressure detecting diaphragm via the pressure transmitting member in a state where the flow passage unit is mounted on the pressure detection unit by the mounting unit, and
• wherein the outer diameter of the pressure transmitting member is 0.2 times or greater and 0.6 times or less of the inner diameter of the communication hole.