It was found that a compound according to the following formula: or a pharmaceutically acceptable salt thereof, has a strong antagonism for both the 5-HT2B and 5-HT7 receptors. In addition, the compound shows good pharmacological action as compared to antagonists selective for only one of these receptors. Based on the above, the compound of the present invention is useful for the prevention and/or treatment of diseases in which 5-HT2B receptor and 5-HT7 receptor are concerned, particularly for the treatment of irritable bowel syndrome (IBS).