To provide a mass measuring instrument for measuring precisely and quickly a mass of an object to be measured, by a method not depending on a differential method, while taking viscus friction into consideration, when a measuring block is damped-oscillated by an influence of the atmosphere or friction.

This mass measuring instrument is provided with an oscillation block swung by mounting the object to be measured, a physical quantity converting means for converting a displacement amount of the oscillation block into an electric signal to be output, a signal processing means for estimating a mass of the object to be measured by integrating the electric signal output from the physical quantity converting means, and an output means for outputting the mass of the object to be measured estimated by the signal processing means. A displacement amount corresponding to the object to be measured is output and a differential equation is used, in a conventional mass measuring technique, but a sampled signal gets to pseudo-differentiation because the signal is not smooth, and an error is generated thereby not to be measured precisely. By this reason, the frequency is estimated quickly and precisely by the integration processing by the signal processing means, and the mass is measured based on a frequency estimation result, in the mass measuring instrument of the present invention.