An apparatus for mapping multiple lower-speed signal transmission frames to a higher-speed signal transmission frame. The apparatus includes buffers configured to buffer the lower-speed signal transmission frames, determination units configured to determine frequency justification information for the lower-speed signal transmission frames, a barrel shifter configured to receive signals output from the buffers, and a controller configured to control the barrel shifter to map the lower-speed signal transmission frames to the higher-speed signal transmission frame based on external settings for the respective lower-speed signal transmission frames and the frequency justification information determined by the determination units. When the minimum unit of the lower-speed signal transmission frames is a channel, the number of the buffers and the number of the determination units correspond to the maximum number of channels that can be multiplexed in the higher-speed signal transmission frame.