To supply digital audio data to an audio device by efficiently converting a size of 1 word of the digital audio data on a computer bus.

Each of 8-bit data at a high-order and a middle-order of an L channel are called from an FIFO memory of a data bus, latched by a latch 112 (middle-order L channel), a latch 113 (high-order L channel), 8-bit data of the low-order L channel and 8-bit data of high-order R channel are called from the memory and latched by a latch 111 (low-order L channel), a latch 116 (high-order R channel) and of 8-bit data of the middle-order R channel and 8-bit data of low-order R channel are called from the memory and latched by a latch 114 (low-order R channel), a latch 115 (middle-order R channel). Then, the 8-bit data latched in the latches 114 (high L), 112 (middle L), 111 (low L), 116 (high R), 115 (middle R), 114 (low R) are read simultaneously and become parallel 24-bit data of the L, R channels, which are fed to parallel serial conversion circuits 12L, 12R, where they are respectively converted into L, R channel audio serial data and outputted.