PROBLEM TO BE SOLVED: To provide a medium for promoting cell proliferation, containing FGF1/FGF2 chimeric protein having high stability against temperature fluctuation and resistance to a proteolytic enzyme as an active ingredient.SOLUTION: The medium for promoting the cell proliferation, containing the FGF1/FGF2 chimeric protein having the high stability against temperature fluctuation and the resistance to the proteolytic enzyme as an active ingredient contains the chimeric protein comprising an amino acid sequence represented by a specific sequence in the FGF1/FGF2 chimeric protein as the active ingredient.【課題】温度安定性及び蛋白質分解酵素抵抗性の高いFGF1/FGF2キメラ蛋白質を有効成分とする細胞増殖促進用培地を提供する。【解決手段】FGF1/FGF2キメラ蛋白質のうちの特定の配列で表されるアミノ酸配列からなるキメラ蛋白質を有効成分とすることで、温度安定性及び蛋白質分解酵素抵抗性の高いFGF1/FGF2キメラ蛋白質を有効成分とする細胞増殖促進用培地。【選択図】なし