Disclosed is a magnetic induction power supply device, which switches the unit coil having the smallest number of windings to a rectification unit at the initial operation, thereby preventing the parts damaged due to an excessive inrush voltage. The disclosed magnetic induction power supply device switches the unit coil having the smallest number of windings to the rectification unit when emergency power is applied from a first power supply unit or a second power supply unit. The second power supply unit can supply the power source induced in the unit coils to a sensing unit as the emergency power.