An aptamer that includes a sequence (i) represented by the following formula (IA)That binds to il-17 to inhibit binding of il-17 and the il-17 receptor: G (m) G (m) G (m) and (m) (m) G (x1), C (m) C (m) G G (m) (X) G (x5) G (m) (m) G (x5) u (f) C (X7) (x2) G (x6) u (f) R (x3) (x3) u (m) C (m) G (m) G (m) or (X7)A c (m) (m) (m) c c (m) where a, G, C, and u are each a RNA where the base is adenine, guanine, cytosine and uracil, respectively, where r is an RNA base is adenine or guanine, ,G and C are each an RNA or DNA where the base is adenine, guanine and cytosine, respectively, or is where the RNA base uracil is,Where is a DNA base uracil or thymine in DNA base is where the brackets indicate a change in nucleotide nucleotide (m) indicates that when the nucleotide is a RNAA hydroxyl Group at the 2 position of the ribose in the same is replaced by a Methyl group or (f) indicates that when the nucleotide is a RNAA hydroxyl Group at the 2 position of the ribose in the same is replaced by a Fluorine Atom, (x1) indicates that the nucleotide is without modifying or fosforotioado,Or when the nucleotide is a RNA, a hydroxyl Group at the 2 position of the ribose in the same is replaced by a Fluorine Atom, (x2) indicates that the nucleotide is unchangedOr when the nucleotide is a RNA, a hydroxyl Group at the 2 position of the ribose in the same is replaced by a Fluorine Atom, (x3) indicates that the nucleotide is unchangedOr when the nucleotide is a RNA, a hydroxyl Group at the 2 position of the ribose in the same or is replaced by a Methyl Group (x4), indicates that the nucleotide is unchangedOr when the nucleotide is a RNA, a hydroxyl Group at the 2 position of the ribose in the same is replaced by a Fluorine Atom or a Methyl group or,(x5) indicates that the nucleotide is without modifying or fosforotioado (x6), indicates that the nucleotide is without modifying or fosforotioado, or when the nucleotide is a RNAA hydroxyl Group at the 2 position of the ribose in the same or i
