A data output circuit of a semiconductor memory device includes a pipe latch unit configured to store input parallel data and align the stored data in response to a plurality of alignment control signals to output serial output data, and an alignment control signal generating unit configured to generate the plurality of alignment control signals in response to a burst-type information and a seed address group, wherein the alignment control signal generating unit generates the alignment control signals to swap data in a swap mode where the burst-type is a certain type and bits of the seed address group are certain values.