The present invention aims to provide a novel low-molecular-weight compound having an orexin agonist activity, which is expected to be useful as a superior agent for the treatment or prophylaxis of narcolepsy. The present invention provides a compound showing superior orexin agonist activity which is represented by the formula (I)wherein each symbol is as defined in the DESCRIPTION, and a pharmaceutically acceptable acid addition salt thereof, as well as an orexin agonist containing the compound or a pharmaceutically acceptable acid addition salt thereof.
