The present invention provides an electrostatic discharge protector capable of taking measures for electrostatic discharge against electronic wiring boards having various designs freely, simply and easily, having excellent accuracy of regulating an operating voltage and capable of being downsized and decreased on its cost, and also provides a resin composition for a discharge gap capable of preparing the electrostatic discharge protector. The resin composition for filling a discharge gap of an electrostatic discharge protector comprises a resin having a urethane structure represented by the formula (1): wherein plural R's are each independently an alkylene group of 1 to 18 carbon atoms, X is a bivalent organic group and m and n are each independently an integer of 1 to 20. The electrostatic discharge protector is obtainable by filling the discharge gap with the resin composition. The discharge gap has a width of 2 to 10 μm.