A light interference measuring device comprises: a light source 20 that outputs light; a beam splitter 222 that causes the light output from the light source to diverge into a reference optical path and a measurement optical path and that outputs a combined wave in which reflection light that has passed through the reference optical path and reflection light that has passed through a measuring object arranged in the measurement optical path are combined; a reference mirror 231 that is arranged in the reference optical path and that reflects light which is diverged into the reference optical path by the beam splitter 222; a stage 12 that is arranged in the measurement optical path and that has the work W placed thereon; an imaging part 25 that images an image in which the combined wave is formed; a reference mirror adjustment mechanism (234, 238, 239) that adjusts a posture of the reference mirror 231; and a control part that controls the reference mirror adjustment mechanism such that a reflecting surface of the reference mirror 231 corresponds to a measurement surface of the work W, based on an image imaged in a condition where a work W is placed on the stage.