A multi-functional power supply device comprises: a secondary cell, a charging circuit, a controller, and a first connection unit. The secondary cell is used to store electrical energy, and produces a first voltage and a second voltage. When the first connection unit is electrically connected to a solar board, the charging circuit receives the electrical energy which is transformed from the solar board and is then stored in the secondary cell. The controller controls the second voltage to produce at least one output voltage to an application apparatus. Moreover, when the first connection unit changes to connect with a lighting device, the secondary cell provides the first voltage to the lighting device directly. Hence, the present invention provides power to the application apparatus, and produces a light source through the lighting device at the same time.