The present invention aims to provide a biodegradable vascular embolization material that is less likely to coagulate and has an improved flexibility, and whose particle shape is recovered after its passing through a catheter or the like. The present invention provides a biodegradable particle comprising 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 the ratio of the mass of the structure composed of hydroxycarboxylic acid a2 to the mass of the biodegradable copolymer is 30 to 90% by mass.
