An object of the present invention is to provide a solid dispersion that suppresses the reduction of the active ingredient content accompanying oxidation or decomposition of rapamycin or a derivative thereof, can ensure long-term stability, and has high safety. According to the present invention, there is provided a method for producing a solid dispersion comprising rapamycin or a derivative thereof as an active ingredient, the first solvent being a protic polar solvent, the second solvent being an aprotic solvent, and a water-soluble polymer carrier. And rapamycin or a derivative thereof, which includes a first step in which the ratio of the first solvent is higher than 50% by volume of the total volume of the first solvent and the second solvent, and a second step of removing the solvent. A method for producing a solid dispersion is provided.本発明は、ラパマイシン又はその誘導体の酸化や分解に伴う有効成分含量の低減を抑制し、長期安定性が確保でき、且つ安全性が高い固体分散体を提供することを課題とする。本発明によれば、ラパマイシン又はその誘導体を有効成分とする固体分散体の製造方法であって、プロトン性極性溶媒である第１溶媒、非プロトン性溶媒である第２溶媒、水溶性高分子担体及びラパマイシン又はその誘導体を混合する工程であり、第１溶媒の割合が第１溶媒と第２溶媒の総容量の５０容量％よりも高い第１工程、溶媒を除去する第２工程、を包含する固体分散体の製造方法が提供される。
