Provided is a pressure detection device which includes a pressure detection unit and a flow passage unit. The pressure detection unit includes a pressure sensor including a diaphragm and a first connection portion joined to the diaphragm. The flow passage unit includes a diaphragm and a second connection portion joined to the diaphragm. One of the first connection portion and the second connection portion is formed of a magnet, and the other of the first connection portion and the second connection portion is formed of a magnet or a magnetic body. In a state where the flow passage unit is mounted on the pressure detection unit, the first connection portion and the second connection portion are disposed in a state where the first connection portion and the second connection portion are attracted to each other by a magnetic force.
