The present invention relates to novel quinazolinone derivatives inhibiting PI3K; a method for preparing the derivatives; and a pharmaceutical composition for treating hematologic neoplasms or liver diseases, containing the quinazolinone derivatives, wherein the novel quinazolinone derivatives according to the present invention have a beneficial effect in the treatment of hematologic neoplasms or liver diseases. Particularly, the quinazolinone derivatives inhibit PI3Kδ with high selectivity compared to that of a conventional anticancer drug of PI3Kδ inhibitors, thereby significantly reducing immunotoxicity, or simultaneously inhibit PI3Kδ and PI3Kγ, thereby enabling the treatment of autoimmune diseases, and anticancer therapy for blood cancer and the like. These targeted drugs have reduced side effects. The present invention provides a compound represented by Formula 1 or a pharmaceutically acceptable salt thereof, wherein X is —H, halogen, —CH3, or —NH2; and Y is C1-2 linear alkyl or C3-4 cycloalkyl.