A semiconductor device includes: a first driver that drives an output element constituting a switching output stage; at least a part of a bootstrap circuit that generates a boot voltage higher than a switching voltage output from the switching output stage and feed the boot voltage to the first driver; and a boot voltage detection circuit that charges the boot voltage on sensing, with the output element off, the difference between the boot voltage and the switching voltage becoming lower than a lower-limit detection value. The boot voltage detection circuit senses the boot voltage through resistance voltage division if a rectification element constituting together with the output element the switching output stage is on, and senses the boot voltage through capacitance voltage division if the rectification element is off.