A switching power source device including a drive pulse generating circuit configured to output a drive pulse whose pulse width is modulated at a predetermined switching frequency, an inverter circuit having a switching element configured to turn on and off a direct current input voltage in accordance with the drive pulse from the drive pulse generating circuit, to generate an alternating current voltage, and a rectification and smoothing circuit configured to rectify and smooth the alternating current voltage, to generate an output voltage, and to supply an output current to a load, the switching power source device further comprising: current control pulse generating means configured of a target value setting module configured to output a value which, being a predetermined target value relating to a control of the output current, can be changed, a computing module configured to carry out a computing process relating to the control of the output current based on the target value, and to output a result of the computation, and a pulse generating module configured to generate a current control pulse voltage for controlling the output current based on the computation result; a current detecting circuit configured to detect the output current from the rectification and smoothing circuit or a current flowing in the switching element, and to output a current detecting voltage based thereon; and a current limit signal generating circuit which, when the current detected by the current detecting circuit exceeds a reference value set based on the output of the current control pulse generating means, is configured to output a current limit signal for limiting the current, wherein the drive pulse generating circuit is configured, on the current limit signal being output, to operate in such a way that an on-duty of the drive pulse driving the switching element stops widening, or becomes narrower, and wherein the current control pulse generating means is configured of a digital processor configured in such a way that the current control pulse voltage can be output as a signal with modulated pulse widht, characterized in that the device comprises a pulse smoothing circuit configured to smooth the current control pulse voltage, generating a smoothed voltage, wherein the current limit signal generating circuit comprises a comparison circuit configured to compare a reference voltage as said reference value determined based on the smoothed voltage and the current detecting voltage, and to output the current limit signal when the current detecting voltage exceeds the reference voltage. current control pulse generating means configured of a target value setting module configured to output a value which, being a predetermined target value relating to a control of the output current, can be changed, a computing module configured to carry out a computing process relating to the control of the output current based on the target value, and to output a result of the computation, and a pulse generating module configured to generate a current control pulse voltage for controlling the output current based on the computation result; a current detecting circuit configured to detect the output current from the rectification and smoothing circuit or a current flowing in the switching element, and to output a current detecting voltage based thereon; and a current limit signal generating circuit which, when the current detected by the current detecting circuit exceeds a reference value set based on the output of the current control pulse generating means, is configured to output a current limit signal for limiting the current, wherein the drive pulse generating circuit is configured, on the current limit signal being output, to operate in such a way that an on-duty of the drive pulse driving the switching element stops widening, or becomes narrower,