A power supply device includes a current sensor detecting a current flowing between a junction, where an output of a first boost converter and an output of a second boost converter are joined together, and a load circuit, and a control device controlling the first and second boost converters and monitoring a current value detected by the current sensor. The control device performs pulse width modulation control over the first and second boost converters based on carrier signals equal in frequency and different in phase. The control device obtains an individual value of currents flowing through the first and second boost converters by sampling the detected current value with a time difference corresponding to phase difference.