To provide a cyclopropylamine derivative useful as an inhibitor of a histone demethylation enzyme KDM1A.SOLUTION: There is provided a compound of the formula (I). In the formula, A, R, and Rare aryl or the like.SELECTED DRAWING: None【課題】ヒストン脱メチル化酵素KDM1Aの阻害剤として有用なシクロプロピルアミン誘導体の提供。【解決手段】式(I)の化合物。式中、A、R1、R2はアリール等。【選択図】なし