A data buffer device includes: a tag value generation circuit that generates a tag value; a first buffer that stores first priority data; a second buffer that stores second priority data; and a data output circuit that outputs the first priority data or the second priority data, wherein the tag value generation circuit sets a tag value for the following second input data to a second tag value which differs from a first tag value for second preceding input data, and sets a tag value of the following first input data to a fourth tag value that is the same as a third tag value for the first preceding input data, and wherein the data output circuit outputs the first priority data or the second priority data in a first mode based on the tag values and outputs the first priority data earlier in a second mode.