PURPOSE: To provide an inexpensive and highly reliable flow meter with a higher dimensional accuracy by integrating a metal pipe for reinforcing subjected to screwing work and a drawn molded pipe using a glass fiber base material into a die for molding to mold in a one-piece structure at joint parts on the inlet and outlet sides of an instrument body.

CONSTITUTION: A short tubular metal pipe mounting member 81 for a piping on the inlet side communicating with a measuring chamber 7 of a capacity type flowmeter body 1 and an identical mounting member 82 on the outlet side are molded in a onepiece structure by a die. Outer screws 31 and 32 are machined previously on the joint members to be connected to the pipings. Non- circular gear-shaped rotary elements 61 and 62 mated with each other are mounted in the measuring chamber 7 with shafts 51 and 52 respectively free to turn. Here, the metal pipe mounting members 81 and 82 can employ a drawn molded product or a laminated molded pipe using a glass fiber base material comparable to a metal material in the respect of strength.