In a resistance plate, a first slide portion includes a plurality of first conductive segments arranged at intervals generally in a direction of sliding movement of a sliding arm, the adjacent first conductive segments being connected together via a resistor. A first conducting path 13 extends between the first slide portion and a first end land to electrically connect them together, the first end land being provided for detecting a quantity of electricity appearing according to the positions of the first conductive segment and a second conductive segment which are held in contact with the sliding arm. A protector is formed on the first conducting path to cover this first conducting path. The protector and the resistor are made of the same material.