An electric connection box 10 comprises an FET 32 for connection with a power supply B, a substrate side conduction path 18 connected with the FET 32 and connecting the FET 32 with a load L, a diode element D connected with the substrate side conduction path 18 electrically and to transfer heat and having a PN junction, and a CPU 19 for judging whether the voltage drop value between the input/output terminals 25 and 26 of the diode element D is larger than a threshold or not and delivering an off-command signal to the FET 32 if a judgment is made that the voltage drop value is smaller than the threshold.