A film thickness measurement apparatus includes: a stage that places a substrate having a film formed thereon and measures a thickness of the film in-situ in a film forming apparatus; a film thickness meter including a light emitter that emits light toward the substrate disposed on the stage and a light receiving sensor that receives the light reflected by the substrate for measuring the thickness of the film in-situ; a moving mechanism including a multi-joint arm that moves an irradiation point of the light on the substrate; a distance meter that measures a distance between the light receiving sensor and the irradiation point on the substrate; and a distance adjustor that adjusts the distance between the light receiving sensor and the irradiation point on the substrate.