Provided are an apparatus and a method for processing MIDI in a wireless terminal capable of controlling a volume of sound source samples when the MIDI is played. According to the method, a plurality of notes, volume levels, volume section information, and note playback duration information are extracted from an inputted MIDI file. After a volume sample number in each section is calculated using the extracted volume level and the volume section information, a volume of the sound source samples that correspond to a note that is to be played is controlled using the volume sample numbers. Next, frequency of the sound source samples are converted to a frequency assigned to the notes and the sound source samples are outputted, reducing a system load caused by the real-time play of the MIDI.