A piezoelectric unit 1 includes a piezoelectric element that causes thickness shear vibration, a first electrode provided on one surface of the piezoelectric element, a second electrode and a third electrode which are provided on an opposite surface to the one surface which is provided with the first electrode of the piezoelectric element and are electrically insulated from each other, and a switching portion that is connected to the first electrode, the second electrode, and the third electrode, in which the switching portion can switch measurement modes between a mass/viscoelasticity measurement mode for measuring mass of a substance which is in contact with the piezoelectric element or viscoelasticity by vibrating the piezoelectric element, and an electrical characteristic measurement mode for measuring electrical characteristics between the second electrode and the third electrode.