PURPOSE: To provide a port unit of commonly used type which has the primary side port and secondary side port and which can serve as any of a filter, regula tor, and filter regulator.

CONSTITUTION: In the first mounting part 6 of a unit body 1a, a filter accommodating vessel is installed which encloses a filter element when the port unit concerned 1 is used as a filter or a filter regulator, and a cap for regulator is installed when the unit is used as a regulator. In the second mounting part 10 of the unit body 12a, cap for filter is mounted when the port unit 1 is used as a filter, and a pressure regulator is mounted when the unit is used as a regulator or a filter regulator. Thereby the same port unit 1 can serve as filter, regulator, and filter regulator commonly.