ABSTRACTOrnamentation, which had been an essential part of Western music for centuries, was systematized and reached the climax during the Baroque period (17th∼18th C). In this period, ornamentation was largely left to the performers so that they could add appropriate ornaments according to their taste and ability. On the other hand, composers often indicate definite ornaments by some sort of written sign or written-out notes to enhance the level of expression and give life to music. For either case, since musical style of the period was commonly understood at that time, there was little problem in performance. However, it is difficult for contemporary performers to relate to performance practices of the Baroque period. The traditions from those times have been broken not to exist to the present, and as a result the expressive qualities of the music have been diminished. In order to overcome such problems, performers should understand the nature of Baroque ornamentation and properly apply it to the music which they play. In this respect, this study provides the guidelines for application of Baroque ornamentation. Firstly, general principles of the five principal Baroque ornaments - slide, trill, appoggiatura, mordent, and turn -were investigated. Secondly, focusing on J. S. Bach's organ music, it was analyzed how he used those ornaments in his works. Finally, those findings from general investigation and specific analysis of Bach's ornamentation were applied to his Organ Sonata No. 1 Eb Major, 2nd movement, BWV 525. In this piece, while Bach indicated only two ornaments, two-note slide and appoggiatura in the first and third measure respectively, other ornaments such as trill, mordent, and turn as well as additional slides and appoggiaturas could be applied. This is only an example of how to apply ornamentation to the Baroque music, and its variaton is surely possible. However, there is no doubt that adding and applying ornamentation to the Baroque music in the proper and logical ways will be indispensible and consequently enhance the quality of music.