To provide an apparatus for measuring trace mass, using a simple structure which uses a piezoelectric vibrator, such as a quartz crystal or the like as a sensor, and in which the resonance frequency of a flow channel, with a sample solution flowing therethrough, will not be affected by the longitudinal wave vibrations caused by the piezoelectric vibrator and propagating through the liquid phase.

The apparatus for measuring trace mass is equipped with the flow channel, through which the sample solution flows; the piezoelectric vibrator installed inside the flow channel; and a vibration absorber which is disposed near the piezoelectric vibrator and absorbs the longitudinal wave vibrations caused by the piezoelectric vibrator.