In order to improve the noise immunity of vortex flowmeters, we have investigated the hydrodynamic vibration around the bluff body of the flowmeter. We used numerical approaches to visualize the time dependent vortex motion within the channel of the flowmeter, and experimental approaches to clarify the characteristic of the hydrodynamic vibration on the side faces of the prismatic bluff body. The results show that the hydrodynamic vibrations with 180° phase shift occur on the side faces of the bluff body, i.e. the prism. The most intense vibration points are situated here. By using differential transducers, a vortex flowmeter with improved measurement accuracy has been developed.