To provide an input protection circuit capable of protecting an electrical apparatus which operates on direct-current power without fail even if the electrical apparatus is used to meet recent needs.

The protection circuit 1 is for protecting an electrical apparatus 5 if the electrical apparatus is connected with a direct-current power supply 6 with the positive and negative polarities by mistake. The protection circuit 1 to be formed between the power supply 6 and the electrical apparatus 5 comprises a diode 2 and an overcurrent protection and prevention element 3. The diode 2 is connected in series with the positive input end 5a of the electrical apparatus 5 so that the diode is in forward direction to the positive terminal 6a of the direct-current power supply 6. The overcurrent prevention element 3 of the protection circuit 1 is connected in series with the negative input end 5b of the electrical apparatus 5.