Novel compound having affinity for amyloid

Disclosed is a compound having affinity for amyloid and satisfactorily rapid clearance from a normal tissue and reduced in toxicity including mutagenicity. Specifically disclosed are: a compound represented by the formula (1) and a salt thereof; and a low-toxic diagnostic agent for Alzheimer's disease comprising the compound or the salt thereof. (1) wherein R represents a group selected from a hydrogen, a hydroxyl group, a carboxyl group, a sulfate group, an amino group, a nitro group, a cyano group, an alkyl substituent group having 1 to 4 carbon atoms and an alkoxy substituent group having 1 to 4 carbon atoms; R represents a radioactive halogen substituent group; and m represents an integer ranging from 0 to 2.