The piano works of Claude Achille Debussy (1862-1918) as well as the works of Beethoven, Schumann, Chopin, Liszt constitute an important repertoire for the pianists. What is common among their works would be that they were composed in consideration for almost all the functions of pianos that had been improved by leaps and bounds since the latter half of the eighteenth century. Debussy is generally called an "impressionist" composer. As everyone knows, this word as well as "baroque" is a historical word of music borrowed from the history of art. Therefore, it is needless to say that having knowledge about impressionist painters is necessary in playing the piano works of Debussy. Then I wonder what kind of relationship there is between them. I wonder what it is like if there is a relationship. It is the purpose of this article to give a concrete consideration on the way of playing the piano, taking up his piano works in order to approach these tasks. Piano techniques were used to create a certain definite "form" to perfection with melody and vigor in the piano works of Beethoven, Schumann, Chopin, Liszt whereas in those of Debussy, it can be said that they were used to show, so to speak, "impressionistic" expressive spirit, representing a world of sound whose "form" is vague. One of the great features is seen in the use of soft pedal.