This invention controlled provides release particles 1 which include a core2 obtained by miniemulsion polymerization of a core ingredient component containing an antibiotic compound having hydrophobic and a fist polymerizable vinyl monmer having hydrophobic, and containing a homogeneous phase of a first polymer formed by a first polymerizable vinyl monomer and the antibiotic compound present in the first polymer that have compatibility with each other and a shell 3 obtained by the core 2 is used as a seed in a seed micro-suspension polymerization of a shell ingredient component containing a second polymerizable vinyl monomer, and covering the core 2.本發明之持續釋放性粒子1具備:將含有疏水性抗生物活性化合物及疏水性第1聚合性乙烯單體之核芯原料成分藉由微乳化液聚合獲得之核芯2,在藉由第1聚合性乙烯單體之聚合獲得之第1聚合物中含有抗生物活性化合物為相溶之均一相之核芯2;及將含有疏水性第2聚合性乙烯單體之殼層原料成分藉由將核芯2作為種子之種子乳化聚合獲得之殼層3,將核芯2包覆之殼層3。1‧‧‧持續釋放性粒子2‧‧‧核芯3‧‧‧殼層
