To provide a protection circuit for a load circuit which can distinguish between an overcurrent generated at a load and a rush current generated at the time of turning on a semiconductor switch or switches provided on the downstream side of the semiconductor switch and can turn the semiconductor switch off only when the overcurrent is generated to thereby protect the load circuit. A comparator CMP1 compares a detection current I1 detected by an ampere meter 15 with a threshold current Iref set in advance. When the detection current I1 reaches the threshold current Iref, the semiconductor switch 11 is turned off to thereby protect the load circuit. Further, a voltage Vd on an electric wire coupling between a battery VB and the semiconductor switch 11 is measured. When a counter electromotive force is generated and the voltage Vd reduces, the threshold current Iref is reduced according to the voltage reduction. Thus, at the time of the occurrence of a dead short, the detection current I1 immediately reaches the threshold current Iref to thereby turn the semiconductor switch 11 off. At the time of the generation of a rush current, since the detection current I1 does not reach the threshold current Iref, the generation of the erroneous turning-off can be prevented.