Provided is a novel compound which has an excellent Aβ aggregation inhibitory effect and is useful as a pharmaceutical. An amide compound represented by the formula (1) or a salt thereof, wherein Z represents CH or N; A and B are the same or different and each represents —CH2—, —O—, —S—, or —NH—; R1 and R2 are the same or different and each represents a branched alkyl group, a branched alkenyl group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aralkyl group, an optionally substituted cycloalkyl group, or an optionally substituted aromatic heterocyclic group; and R3 represents a branched alkyl group, a branched alkenyl group, an optionally substituted cycloalkyl group, or an optionally substituted aralkyl group.