A remote sensing apparatus includes an optical system device, a frequency converter, and a frequency analyzer. The device transmits laser light generated from a laser light source toward an optical pattern rotary plate to receive its reflection light by an optical receiver. The plate is a measurement object. The converter converts a reception signal obtained by the receiver into a signal in a frequency domain. The analyzer analyzes a frequency component of the signal obtained by the converter, selects candidate values of sideband wave frequencies from the signal in the frequency region, obtains an approximate value of a rotational frequency by decision of a majority of intervals of the sideband wave frequencies, obtains candidate values of the carrier frequency from the approximate value, and selects the rotational frequency on the basis of the candidate values of the rotational frequency from among the candidate values of the carrier frequency.