A pre-set variable passive element can prevent faulty insulation between itself and a conductive board. A cylindrical member extended higher than a adjusting member is made of ceramic around the adjusting member which is rotatably fitted for adjustment of the value of resistance of the pre-set variable resistor element, the forming of the cylindrical member being integrally formed with a main part also formed in a ceramic. The cylindrical member is fitted into an opening bored in a stator board mainly of a steel plate, and the pre-set variable resistor is fitted on the stator board. The adjusting member which is contacted by a contact, by which the value of resistance of the pre-set variable resistor element is determined, and an inside periphery of the opening free from any insulating treatment is securely insulated by the cylindrical member.