A semiconductor device operates with electric power supplied from a direct-current power supply to an internal circuit in a state where a bypass capacitor is connected to a power supply terminal. The semiconductor device includes a load current control unit and a detection unit. The load current control unit changes an electric current supplied from the power supply terminal only in a predetermined operation period. The detection unit detects a voltage of the power supply terminal. The detection unit outputs a detection signal when the voltage is higher than a threshold upper limit in a case of being provided with the threshold upper limit. Alternatively, the detection unit outputs a detection signal when the voltage is lower than a threshold lower limit in a case of being provided with the threshold lower limit.