Provided is a biodegradable resin composition having a high degradation rate. The biodegradable resin composition is a biodegradable resin composition having water holding properties. The biodegradable resin composition preferably contains a biodegradable resin and is preferably capable of holding 0.007 g or more and 15.0 g or less of water relative to 1 g of the biodegradable resin. The biodegradable resin composition preferably contains a seaweed-derived polysaccharide as a hydrolysis accelerator that improves the water holding properties and accelerates hydrolysis of the biodegradable resin. The seaweed-derived polysaccharide is preferably, for example, fucoidan, laminarin, alginic acid, or an alginate. The biodegradable resin composition preferably contains a photocatalytically active substance that degrades the biodegradable resin.