To provide a light control device which has a plain circuit configuration and which is small and highly reliable.

The light control device 100 is equipped with PWM circuit 401 for driving by pulse width modulation and a switching device 110 formed on the same chip. The switching device 110 has a driving circuit 111, a superheating block protection network 306, a semiconductor switch, the main control FETQA, the first reference FETQB for reference voltage formation, and a resistor Rr1. Further, an over-current detecting means is realized by a comparator CMP1 or the like which detects the difference between a reference voltage and voltage between drain sources of the main control FETQA. By being cut-off controlled of the drive circuit 111 by this output, the main control FETQA becomes controlled on/off. The over-current detecting means and the on/off control means becomes to have a soft start function to suppress rush currents into loads 102a to 102n of a lighting system in combination.