The present invention relates to a pharmaceutical composition for preventing or treating neurodegenerative diseases by targeting a specific miRNA. In addition, the present invention relates to a kit for diagnosing neurodegenerative diseases. A miR-206 target found in the present invention, which is highly expressed in both animal models of Alzheimer's disease and human brain samples, is a substantial treatment target selected without artifact errors. An antisense oligonucleotide of the present invention as an inhibitor for miR-206 suggests a successful result in treatment of neurodegenerative diseases by targeting miRNA. The antisense oligonucleotide of the present invention inhibits the function of miR-206 to greatly increase the levels of BDNF and IGF-1 and to increase the regeneration of synapses, thereby treating neurodegenerative diseases, particularly Alzheimer's disease.