A load controller according to an embodiment includes a switching unit, a power source unit, and a control unit. The switching unit controls supply of power from an AC power supply to a load by selectively connecting or disconnecting the load to/from the AC power supply. The power source unit converts AC power supplied from the AC power supply into DC power. The control unit operates with the DC power supplied from the power source unit and controls the switching unit. The power source unit includes a constant-voltage source and a constant-current source. The constant-voltage source keeps a DC voltage to be output to the control unit a constant voltage. The constant-current source keeps a DC current to be supplied via the constant-voltage source to the control unit a constant current.