PURPOSE: To obtain a fluid sensor employing transverse wave in which an enclosing member can be selected freely by enclosing a liquid under test in order to prevent adverse effect, e.g. corrosion of a converting means, thereby preventing a transverse wave from being damped at the enclosed part.

CONSTITUTION: A substrate 56 comprises a detecting region, and electrode fingers 60, 62, 64, 66 for transmitting a shearing transverse wave along the detecting region, and provided with a flow cell 12. A liquid to be tested is fed into the flow cell and held in a flow region 34 by means of a gasket 32. The electrode fingers at the gasket part have different width and thickness so that the shearing transverse wave can permeate deeper than others thus suppressing the damping of the transverse wave.