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 focussed onto the light detector ( 12 ) by an optical system ( 8 ). A signal corresponding to the geometric center or the maximum (I₀) of the intensity distribution of the focussed measuring spot is determined based on the measured values obtained by the light detector ( 12 ).