To provide a simple protective relay which properly protects a load even in the absence of such a mechanism as a bimetal.

A protective relay 20, which issues a failure signal when a current that keeps flowing in a load becomes greater than a predetermined one, includes heating elements 24, 25, 26, which covert the current flowing in the load to heat, and heat sensitive elements 124, 125, 126 which are placed near the heating elements 24, 25, 26, have a sharp increase in resistance value with the temperature rise, and have a heat-time constant approximating a heat- time constant that is characteristic of the load 50. Also, the relay has a moving mechanism which varies the distance between the heat sensitive elements and the heating elements by moving either the heat sensitive elements 124, 125, 126 or the heating elements 24, 25, 26.