An interferometric path and/or rotation measuring device has a transducer unit with grating element, which transducer cooperates with a light conductor unit and a light pickup unit to detect a linear and/or rotational movement of the grating element in such a way that two partial beams of the light conductor unit which are aimed at the grating element, generate a superposition signal which is detectable by the light pickup unit and is a function of the linear or rotational movement and/or a position of the grating element. A modulation interferometer unit is connected upstream from the light conductor unit and has an arrangement for beam splitting into the two partial beams.