In an optical movement information detector, light emitted from a laser diode (1) is split into a first beam (10), a second beam (11) and a third beam (12) by beam splitters (2a, 2b). The first, second and third beams are converged by a condenser lens (4) upon a surface of an object to be measured (5) to form a beam spot (13) thereon. Diffused light from the beam spot (13) is received by a photodiode (6) and an output signal of the photodiode (6) is processed by a signal processing circuit (20) including an analog-digital converter (8) and a Fourier transforming unit (9). A detecting section (21) obtains, for example, a moving velocity and a moving direction of the object based on spectrum peak frequencies obtained by the Fourier transform.