A multimedia data reproducing device is provided which includes: a codec converting digital data into an analog signal by a predetermined method and reproducing the analog signal; and a control unit including a core generating a reproduction block by decoding multimedia data and outputting the generated reproduction block to a main memory in an activated state and an interface transmitting the reproduction block stored in the main memory as the digital data to the codec and transmitting the multimedia data stored in an auxiliary memory to the core in an activated state. Accordingly, it is possible to efficiently reproduce multimedia data to reduce the power consumption of a battery by alternately turning on and off a power source of blocks other than the interface in the control unit periodically or depending on a predetermined situation.