To provide accurate vibration measurement by simplifying an optical system and a signal processing system to prevent miscount from occurring in a downsized and weight-reduced device for measuring semiconductor laser digital vibration, and to extract the characteristics of vibration.

The device includes: a semiconductor laser with its laser oscillation frequency fixed; an optical head portion comprising an optical element disposed so that projected light from a semiconductor laser diode is applied to the surface of a vibratory body and its returned light is joined to the semiconductor laser, and a light receiving element for detecting a semiconductor laser output generated in association with displacement of the vibratory body; a circuit having the function of supplying an electric current to the semiconductor laser while detecting a signal component in an output of the receiving element; an AD converter converting an output of a detection part; a circuit having the function of counting the number of Doppler beat waves, having the function of counting and determining a displacement direction from the output of the detection part, and calculating and measuring a count value of a counter part; and a program for controlling a comparison circuit and extracting the features of vibration waveforms.