A biodegradable particle including a block copolymer produced by copolymerization of a biodegradable copolymer having a structure composed of hydroxycarboxylic acid a1, whose homopolymer produced by homopolymerization has a glass transition point of not less than 40° C., and hydroxycarboxylic acid a2, whose homopolymer produced by homopolymerization has a glass transition point of not more than −40° C.; a water-soluble polymer comprising a functional group selected from the group consisting of a hydroxyl group, amino group and carboxylic acid group at each of both ends; and a polyvalent compound comprising 2 or more functional groups each selected from the group consisting of a hydroxyl group, amino group and carboxylic acid group; wherein a ratio of mass of said structure composed of hydroxycarboxylic acid a2 to mass of said biodegradable copolymer is 30 to 90% by mass.