The present invention provides an aptamer binding to an autotaxin, which contains a nucleotide sequence represented by the formula: GWAACAGGUUUUGCU (SEQ ID NO: 42) wherein W is A or U (provided uracil is optionally thymine), and which is the following (a) or (b): (a) an aptamer wherein, in the nucleotides contained in the aptamer, (i) the 2'-position of the ribose of each pyrimidine nucleotide is a fluorine atom, (ii) the 2'-position of the ribose of each purine nucleotide is a hydroxy group； (b) the aptamer of (a), wherein (i) the fluorine atom at the 2'-position of the ribose of each pyrimidine nucleotide is independently unsubstituted, or substituted by an atom or group selected from the group consisting of a hydrogen atom, a hydroxy group and a methoxy group, (ii) the hydroxy group at the 2'-position of the ribose of each purine nucleotide is independently unsubstituted, or substituted by an atom or group selected from the group consisting of a hydrogen atom, a methoxy group and a fluorine atom.
