Abstract: 3-piperidyl-4-oxoquinazoline derivatives are provided, which is represented by the formula (I): wherein R represents an amino group or a cyclic amino group such as dibenzoazepine, each of which is substituted with a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or the like, n is an integer of 1 to 3, R3 and R4 independently represents a hydrogen atom, a lower alkyl group, or the like, or a pharmaceutically acceptable salt thereof. Compounds (I) of the present invention have excellent MTP-inhibitory activity. Thus, these compounds not only inhibit formation of LDL that is a cause of arteriosclerotic diseases but also regulate TG, cholesterol, and lipoproteins such as LDL in the blood and regulate cellular lipids through regulation of MTP activity. They can also be used as a new type of preventive or therapeutic agents for hyperlipemia or arteriosclerotic diseases.