A compound or a salt thereof represented by Formula (I). An LSD1 inhibitor containing the compound or a salt thereof as an active ingredient. A pharmaceutical composition containing the compound or salt thereof. An antitumor agent containing the compound or a salt thereof as an active ingredient.本發明提供一種通式(I)所表示的化合物或其鹽。將該化合物或其鹽作為有效成分之LSD1抑制劑、含有該化合物或其鹽之醫藥組成物以及將該化合物或其鹽作為有效成分之抗腫瘤劑。