To provide a counter-electromotive force prevention unit for batteries, which can prevent the occurrence of noise due to the counter-electromotive force generated by loads of a battery and turning on and off of a charging generator, and which can suppress noise emanating from car audio speakers, electrical products, and malfunctioning of electronic equipment.

A reverse-blocking diode 104 and a fuse 105 that fuses with overcurrent are connected in series between a positive lead wire 102 and a negative lead wire 103 that are connected to the positive terminal and negative terminal of a battery serving as a DC supply source, respectively. A capacitor 106 is connected in parallel with the reverse-blocking diode 104.