PURPOSE: To improve the reliability by allowing a fluid to flow-into a spiral measurement pipe with a double loop, operating the double loop as a tuning fork, and vibrating the forks of the tuning fork freely in opposite phase so that they perform twist vibration as a function of mass flow rate.

CONSTITUTION: A double loop is formed spirally in a channel pipe 10 by a pair of measurement loops 10A and 10B, and isolation loops 10C and 10D are formed on both sides. The double loop is connected to a stiff bar 15 at three junctions, and the loops 10A and 10B effectively operate as a tuning fork with forks that are constituted by the same measurement loop. The forks are vibrated in opposite phase at the natural resonance frequency of the tuning fork, the loops 10A and 10B are subjected to the torque of coriolis in opposite direction when a fluid flows and are twisted so that they approach and are separate each other, where the measurement loop is driven as the gears of the tuning fork by a permanent magnet 16 and a cooperation coil 17 that is connected to the loops 10A and 10B. And, the vibration of the loops 10A and 10B is inputted to preamplifiers 21 and 20 as signal voltages from capacity sensors S1 and S2 and is processed.