A plurality of protective resistors can be easily inserted between circuit forming elements, and opposite ends of each protective resistor can be properly press-contacted to each circuit forming element. The protective resistor can be easily replaced when broken. A resistor array board comprises a porous plate having a plurality of through-holes arranged in array and opening at opposite surfaces thereof; and a plurality of protective resistors removably loosely inserted into the through-holes, respectively. Each of the protective resistors are resiliently retained by an electrically conductive spring element, and opposite ends of each of the protective resistors are press-contacted with the circuit forming elements which are arranged in opposing relation on surfaces of the porous plates.