Patent ID: 8608927

Claim:
An ion sensor comprising: a first electrode plate; a second electrode plate arranged oppositely to the first electrode plate and having one or a plurality of openings; an ion-sensitive film interposed between the first electrode plate and the second electrode plate, blocking up one of sides of the opening of the second electrode plate, and formed continuously from the end of the side of the opening through the inner wall surface of the opening to the outer surface of the second electrode plate; and a sensor support supporting the second electrode plate so that only the ion-sensitive film formed in the opening and on the outer surface of the second electrode plate comes into contact with a test solution at the time of measuring the test solution, characterized in that difference in potential between the first electrode plate and the second electrode plate is measured while the thickness of the ion-sensitive film interposed between the first electrode plate and the second electrode plate is different from the thickness of the ion-sensitive film formed on the outer surface of the second electrode plate.