Beethoven's Op 106 B Flat Major piano sonata is known as "Hammerklavier". This sonat, composed in 1819 corresponds to the mature period of the composer and is believed as one of the most difficult to be played. Allegro which is the first part of the sonata starts with exhibition section (first theme group, second theme group) development section and fugato within development section, development of modulation, finishes again with exhibition (first theme group, second theme group and finally Coda). Except from ordinary sonata forms sonata form following the fugue brings an increase in volume and in addition to that presents two different composition design within one. The reason why this composition is termed as hammer-clavier sonata is because this sonata is pioneer of modern piano. In addition, "Hammerklavier" is defined in literature as Pianoforte of 1820's Vienna. Within this study, it is observed that the material used in the first part is different from other, corresponds to the maturate period of the composer and includes different composition methodologies within the frame of sonata form. Related with the topic it is stressed how sonata form is developed in terms of historically and formal until 1819.