To simplify a structure by surely and stably holding a cantilever, easily and surely making electric contact between the cantilever and the electrode of a holder main body and electric insulation between the cantilever and the holder main body and surely preventing interference with each line.

When the fitting part 3c of a leaf spring 3 is attached to a holder main body 2, the pressing part 3a of a portion L-shaped in section elastically presses a cantilever on the cantilever supporting base 2a of the holder main body 2. At this time, the cantilever 1 is pressed while the pressing surface of the pressing part 3a is nearly in surface-contact with the upper surface of the cantilever 1, and the cantilever 1 is surely and stably attached between the leaf spring 3 and the cantilever supporting base 2. Since the electrode connecting piece of the leaf spring 3 is brought into contact with the electrode 6 of the holder main body 2, the leaf spring 3 functions as a lead plate for conducting a bias voltage to the cantilever 1.