A data input/output device includes a buffer that accumulates data, and a data receiver that receives data input in synchronization with a first clock in accordance with a second clock whose generation source is different from a generation source of the first clock. The data input/output device further includes a data input part that accumulates data received by the data receiver in the buffer, and a data output part that sequentially outputs data accumulated in the buffer at an output interval depending on the amount of data accumulated in the buffer in such a manner that a predetermined data amount is the unit of the output.