Method capable of avoiding data error from incorrect sampling points

Data decoding devices avoiding data error from incorrect sampling points caused by serious interference are disclosed. The data decoding devices receive an analog signal carrying a reference clock and at least one digital data. In the data decoding device, a slicer slices the analog signal at different sampling points by first and second sampling clocks to obtain first and second bitstreams, and the first and second sampling clocks have the same frequency and a predetermined phase difference. A data check unit evaluates whether the first bitstream is erroneous according to an error checking code thereof, outputs the first bitstream if it is error-free, and evaluates whether the second bitstream is erroneous according to the error checking code if the first bitstream is erroneous.