A sensor head has: a sensor head main body which has disposed therein the stepping motor; a holder which has disposed on an upper surface thereof a plurality of crystal oscillators and which is driven for rotation by the stepping motor; and a mask body which is mounted on the sensor head main body so as to cover an upper surface of the holder and which has opened therein a film-forming window faced by one of the crystal oscillators. The sensor head also has: a first electrode fixed to that portion of the sensor head main body which is located right under the film-forming window; and second electrodes which are in electrical conduction with each of the crystal oscillators and which are disposed to protrude under a lower surface of the holder.