A shadowing compensation device for a solar cell module has an input port, an isolated DC-DC power converter, and an output port. The input port is connected to two output ends of a solar cell array including multiple solar cell modules connected in series. The output port is connected to one of the multiple solar cell modules of the solar cell array. When one of the solar cell modules connected to the output port of shadowing compensation device has been shaded, the isolated DC-DC power converter outputs a compensating current to the solar cell module that has been shaded for increasing the output voltage of the solar cell module that has been shaded, and increasing the output voltage and output power of the solar cell array.