CRYSTAL SENSOR

PROBLEM TO BE SOLVED: To provide the crystal sensor, which can improve the stability of the functions and can achieve the long life by preventing the deterioration of an electrode by a material to be measured, can improve the manufacturing workability by alleviating the manufacturing restriction of the electrode and can improve the sensitivity as a sensor furthermore. SOLUTION: A crystal oscillator comprising a crystal oscillator plate 4 and a first electrode 5 and a second electrode 6, which are provided so as to apply the voltages on the crystal oscillator plate 4, is oscillated in electrolyte solution 7, and the changed natural frequency is obtained. The crystal oscillator plate 4 is provided so that only one surface is in contact with the electrolyte solution. The first electrode 5 is provided at the other surface of the crystal oscillator prate 4. The second electrode 6 is provided at the part other than one surface of the crystal oscillator plate 4 under the state, wherein resistance property is provided for the electrolyte solution 7.