To provide an overcurrent protection apparatus which can surely protect a load circuit from an overcurrent with a simple configuration. Supposing that the temperature increasing amount of a semiconductor element caused when the semiconductor element is turned on is ΔTch, the on-resistance value of the semiconductor element (T1) is Ron, the thermal resistance value of the semiconductor element (T1) is Rth_f, the temperature increasing amount of a connecting wiring is ΔTw when a current flows into the connecting wiring (WL), the resistance value per unit length of the connecting wiring is Rw, and the thermal resistance value per unit length of the connecting wiring is Rth_w, ΔTch is obtained based on an expression of ΔTW/ΔTch=Rth_w/Rth_f*Rw/Ron with respect to the temperature increasing amount ΔTw not exceeding a difference between the upper limit of the permissible temperature of the connecting wiring (WL) and the upper limit of an operational peripheral temperature, then a voltage Vds is obtained based on an expression of ΔTch=Rth_f*Vds2/Ron with respect to the ΔTch thus obtained, and the voltage Vds thus obtained is set as a determination voltage.