Provided is a compound useful as an N-type Ca2+ channel blocker. As a result of intensive studies of compounds having an action of blocking N-type Ca2+ channels, the present inventors found that a tetrahydroisoquinoline compound of the present invention having a substituent at the 1-position has an action of blocking the N-type Ca2+ channels, an antinociceptive pain action, an antineuropathic pain action, an abdominal pain-inhibitory action and an opioid-induced constipation-improving action, and the present invention has been completed based on these findings. The compound of the present invention can be used as a pharmaceutical composition for preventing and/or treating various pains such as neuropathic pain and nociceptive pain, headaches such as migraine and cluster headache, central nervous system diseases such as anxiety, depression, epilepsy, cerebral stroke and restless legs syndrome, abdominal symptoms such as abdominal pain and abdominal distension, stool abnormalities such as diarrhea and constipation, digestive system diseases such as irritable bowel syndrome, urinary system diseases such as overactive bladder and interstitial cystitis, etc.
