A sigma receptor-binding agent, which comprises an alkyl ether derivative represented by formula [1] or a salt thereof is provided. wherein R 1 and R 2 , which are the same or different, each represent a hydrogen atom, a halogen atom, an optionally substituted C 1-6 alkyl group, an optionally substituted aryl group, or the like； R 3 represents an optionally protected hydroxyl group or the like； m and n, which are the same or different, each represent an integer of 1 to 6.
