The purpose of the invention is to provide a biodegradable vascular embolization material for which aggregation does not occur easily, pliability has been improved, and particle shape is restored after being passed through a catheter, etc. The invention provides biodegradable particles obtained from a block copolymer wherein: a biodegradable copolymer having structures obtained from a hydroxycarboxylic acid (a1), the glass transition point of the homopolymerized homopolymer of which is 40°C or higher, and a hydroxycarboxylic acid (a2), the glass transition point of the homopolymerized homopolymer of which is -40°C or less； a water-soluble polymer having functional groups selected from the group consisting of hydroxyl groups, amino groups and carboxylic acid groups, on both ends； and a polyvalent compound having two or more functional groups selected from the group consisting of hydroxyl groups, amino groups and carboxylic acid groups, are copolymerized, and the mass percent of structures obtained from the hydroxycarboxylic acid (a2) with respect to the mass of the biodegradable copolymer is 30 - 90 mass%.
