Measuring device mounting position

For work in which reflecting mirrors (or facets (31)) to be mounted on a heliostat 3 coincide with a pseudo toroid (53), an adjustment method of, and a mounting posture measuring device for, accurately measuring mounting postures of the respective facets (31) are provided for performing mounting adjustment efficiently and simply. In a method of installing the reflecting mirrors (or the facets (31)) constituting the heliostat 3 for sunlight condensation, each facet (31) is installed in such so that a reflected laser beam (52) reflected by the facet 31 can reach a virtual passage point (52b) in a laser point measuring unit (12).