The invention provides an aptamer possessing an inhibitory activity against IL-17, as well as a complex comprising an aptamer possessing a binding activity or inhibitory activity against IL-17 and a functional substance (for example, affinity substances, substances for labeling, enzymes, drug delivery vehicles, drugs and the like). The invention also provides a pharmaceutical drug, cell migration inhibitor, diagnostic reagent, detection probe, carrier, labeling agent, and the like comprising the aforementioned aptamer or complex, and methods of detecting and purifying IL-17 by using the aforementioned aptamer or complex.