To simplify constitution for connecting to an external piping system, to easily assemble a Coriolis mass flowmeter, and to reduce the vibration of the external piping and the like to measure a mass flow rate with high accuracy.

In this flowmeter, two parallel flow tubes 1 and (2) are formed by bending a pipe so that a fluid to be measured flows in series. A pipe entrance part from an external connection part 35 connected with an inlet pipe to the inlet of one flow tube (2) is formed by bending it in an L-shape an further bending it in another direction. On the other hand, a pipe outlet part from an external connection part 36 connected with an outlet pipe to the outlet of the other flow tube 1 is formed by bending it in an L-shape and further bending it in another direction so that the pipe entrance part and the pipe outlet part become symmetric. These external connection parts 35 and 36 are arranged on the same axis.