1. An iterative decoding device comprising: a decoder for receiving a set of soft information, iteratively decoding the soft information and updating the set of soft information accordingly to generate a set of updated soft information; a dual-mode determination unit coupled to the decoder for generating a determination result according to the set of updated soft information; and a dual-mode scaling unit coupled to the dual-mode determination unit and the decoder for scaling the set of updated soft information according to the determination result to generate a set of scaled soft information acting as an input of the decoder for next iteration.