A DC/DC converter in which the DC output set voltage can be raised includes a switching transistor arranged to input an external power supply voltage, a smoothing circuit, a switching control circuit to which the internal power supply voltage is supplied and arranged to control the switching transistor, a comparison circuit arranged to compare the DC output voltage with a first reference voltage and to output a selecting signal, first and second linear transistors arranged to input the external power supply voltage or DC output voltage in accordance with the selecting signal, and to output the voltage according to the internal power supply control voltage as the internal power supply voltage, and an error amplification circuit arranged to input the internal power supply voltage, compare the internal power supply voltage with the second reference voltage, amplify the error thereof, and output the internal power supply control voltage.