The object of the present invention is to provide a microsphere which has a slow-release period of from about two weeks to about four weeks following administration, enables a higher content of a drug to be included, suppresses an initial burst of the drug, and enables the drug to be maintained at an optimal, effective blood concentration during the slow-release period. In a microsphere containing a drug and PLGA, the above problems can be resolved by setting: (1) the amount of lactic acid/glycolic acid copolymer per part by weight of the drug to from about 3 to about 10 parts by weight； (2) the microsphere to an average particle size of from about 20 to about 50 µm； and (3) the lactic acid/glycolic acid copolymer to a weight-average molecular weight of from about 10,000 to about 50,000 and to a lactic acid/glycolic acid compositional ratio of from about 75/25 to about 50/50. In addition, the microsphere, by promoting the production of various endogenous repair factors, is useful against various tissue disorders.
