The composition for hard tissue repair of the present invention is characterized by comprising 5 to 98.95 parts by weight of a monomer (A), 1 to 75 parts by weight of a (meth) acrylate polymer (B) and 0.05 to 20 parts by weight of a polymerization initiator composition (C) containing an organoboron compound (c1), with the proviso that the total amount of the components (A), (B) and (C) is 100 parts by weight. The composition undergoes small-scale heat generation during curing and can ensure a sufficient working time.
