A method for optically detecting the position of a moveable test object (10), especially a mirror or reflector, in which a measuring beam (6) produced by a light source (2) is reflected by the test object (10 and reaches a position-sensitive light detector (12) which carrier out a conversion into information corresponding to the position of the test object (10). The invention enables the position of mirrors, especially rotating mirrors, to be quickly measured optically using a simple optical construction. The measuring beam (6) is focused onto the light detector (12) by an optical system (8). A signal corresponding to the geometric center or the maximum (I.sub.0) of the intensity distribution of the focused measuring spot is determined based on the measured values obtained by the light detector (12).