An osteoclast differentiation inhibitor containing a selective antagonist of the 7 nicotinic acetylcholine receptor as an active ingredient, a bone resorption inhibitor by osteoclasts, a bone regeneration promoter and a prophylactic or therapeutic agent for bone resorbable diseases.α7ニコチン性アセチルコリン受容体の選択的拮抗薬を有効成分とする破骨細胞分化抑制剤、破骨細胞による骨吸収抑制剤、骨再生促進剤及び骨吸収性疾患の予防又は治療剤。