A multipurpose transforming device includes a power supply device that has a power import device and a power output device respectively connected with two side of the power supply device. The power import device and the power output device have connectors used for connected with different types of plugs and outlets. The power output device has at least two output lines so as to supply power to several electric device loads. The power supply device includes an AC supply unit, a voltage-regulating unit, a galvanometry unit, a memory and a microprocessor. The AC supply unit transforms alternating current into direct current. The voltage-regulating unit regulates outputting voltage from zero to rated load according to the microprocessor control. The galvanometry unit samples real-time load current and transmits the sampling value to the microprocessor. A memory stores some common rated loads so that the microprocessor compares with sampling value until two groups of value matches. Finally the microprocessor commands the voltage-regulating unit to retain output at the value.