Disclosed is an output buffer circuit including main-data output buffers; a de-emphasis output buffer; and a selector that performs switching control in such a way that, based on a control signal indicating whether de-emphasis is to be enabled or disabled, main data is supplied to the de-emphasis output buffer to make the buffer operate as a main-data output buffer when the control signal indicates that de-emphasis is to be disabled, while emphasis data obtained on delaying the main data by the delay circuit is supplied to the de-emphasis output buffer to make the buffer operate as a de-emphasis output buffer when the control signal indicates that de-emphasis is to be enabled.