To improve the accuracy of the measurement result by calculating the center of gravity on the basis of effective data as many as possible.

The optical measuring device includes an optical system, which projects light onto an object and receives the reflected light, and a means 23 for calculating the center of gravity, which calculates the center of gravity in a time distribution of the intensity of the received light or the center of gravity in a spatial distribution of the intensity of the received light at a photo detecting surface. The center of gravity or a result calculated based on the center of gravity using a determined method is output as measured data from the optical measuring device. Furthermore, the optical measuring device includes a range setting means 251 discriminating the change of the intensity of the received light in the time distribution or the spatial distribution and setting a range to be an object for the calculation of the center of gravity in the time distribution or the spatial distribution on the basis of the result of the discrimination.