An aptamer which can bind to chymase to inhibit the activity of chymase and comprises the nucleotide sequence represented by the formula: XGAUAGANNUAAX (wherein X and X independently represent A or G； and N and N independently represent A, G, C, U or T)； a complex comprising the aptamer and a functional substance (e.g., an affinity substance, a labeling substance, an enzyme, a drug delivery medium, or a medicinal agent)； a medicinal agent or a reagent comprising the aptamer or the complex； a chymase detection method or a chymase purification method characterized by utilizing the aptamer or the complex； and others.
