To provide a composition for repairing a hard structure having low void ratio after curing, and a kit for repairing hard structure.SOLUTION: There are provided a composition for repairing a hard structure containing a monomer (A), a polymer powder (B) and a polymerization initiator (C), in which cumulative ratio of a powder particle with aspect ratio of 1.00 or more and less than 1.10 in whole powder particle of each component contained in the composition for repairing the hard structure is 3.5 cumulative% or less, and a kits for repairing the hard structure having a component in which each component of a monomer containing the composition for repairing the hard structure (A), a polymer power (B) and a polymerization initiator (C) are accommodated as combination with dividing into 3 or more.SELECTED DRAWING: None【課題】硬化後の空隙率が低い硬組織補修用組成物及び硬組織補修用キットを提供する。【解決手段】モノマー（Ａ）、重合体粉末（Ｂ）及び重合開始剤（Ｃ）を含む硬組織補修用組成物であって、硬組織補修用組成物に含まれる各成分のうち粉末粒子全体におけるアスペクト比１.００以上１.１０未満の粉末粒子の累積比率が３.５累積％以上である硬組織補修用組成物；並びに、この硬組織補修用組成物に含まれるモノマー（Ａ）、重合体粉末（Ｂ）及び重合開始剤（Ｃ）の各成分が、任意の組合せで３つ以上に分割されて収容された部材を有する硬組織補修用キット。【選択図】なし
