Disclosed is a compound having a strong affinity to serotonin-4 receptors, which is useful as an enterokinesis-promoting agent or a digestive tract function-improving agent. Specifically, disclosed is a compound represented by Formula (1) or a pharmaceutically acceptable salt thereof. Also specifically disclosed is a pharmaceutical composition containing a compound represented by Formula (1) or a pharmaceutically acceptable salt thereof. [In Formula (1), Ar represents a group represented by Formula (Ar-1) or Formula (Ar-2).]