Disclosed is a semiconductor device for switching power supply control including: a power supply terminal; a current inflow terminal; a starting circuit; and a brownout detection circuit, wherein a control signal of a switching element is generated, the starting circuit includes: a first comparator; a starting control circuit which controls on and off of the switch; and an operation start circuit which detects that the voltage of the power supply terminal becomes equal to or more than a predetermined voltage, and generates a signal for operating an internal circuit, and the brownout detection circuit includes: a voltage divider; a second comparator which has a hysteresis characteristic for detecting generation of a brownout state; a timer circuit which measures a predetermined time during which the generation of the brownout state continues; and an output stop circuit which stops outputting of a switching control signal.