Disclosed is a composition for hard tissue repair, which is characterized by containing 5-98.95 parts by weight of a monomer (A), 1-75 parts by weight of a (meth)acrylate polymer (B), and 0.05-20 parts by weight of a polymerization initiator composition (C) that contains an organic boron compound (c1) (with the total of the components (A), (B) and (C) being 100 parts by weight). The composition generates little heat when cured, and is capable of assuring sufficient working time.本發明的硬組織修補用組成物係包含單體(A)5~98.95重量分、(甲基)丙烯酸酯聚合物(B)1~75重量分、以及含有有機硼化合物(c1)的聚合起始劑組成物(C)0.05~20重量分((A)、(B)、以及(C)之總和為100重量分)。該組成物硬化時的發熱少，而且可確保充分的作業時間。
