PURPOSE: To enable spring constant and dumping coefficient to be measured automatically by a simple circuit composition and a simple operation, by providing a measuring device with a negative return circuit to which load signal, displacement signal and displacement speed signal are put into.

CONSTITUTION: A signal input terminal 10 is connected directly to No.1 multiplier 13 and a signal input terminal 11 is also connected to No.1 multiplier 13 through a comparison point 14, and an output of No.1 multiplier 13 is connected to an integrator 16 through a low-pass filter 15. And output from the integrator 16 is connected to No.2 multiplier 17, and this No.2 multiplier 17 multiplies a signal from a signal input terminal 12 over a signal from the integrator 16 and makes negative return to an input on one side of the No.1 multiplier through the comparison point 14. In this mechanism, if a displacement signal X is put into the input terminals 10 and 12 and also if a load signal f is put into the input terminal 11, the signal d expresses dumping coefficient C.