alpha-Synuclein is a native, unfolded protein that causes several neurodegenerative diseases such as dementia with Lewy bodies and Parkinson's disease. We have now identified the first DNA aptamers against alpha-synuclein using native PAGE applied to the SELEX method. We call this aptamer "M5-15"; it is the alpha-synuclein-bound aptamer and was isolated after four cycles of screening. M5-15 is composed of three stem-loop structures that may play an important role in the binding to alpha-synuclein. Moreover, M5-15 specifically binds to the alpha-synuclein monomer and oligomer. We expect that this aptamer will become a useful tool in alpha-synuclein analysis and diagnosis.