The invention provide a gum base composition which has an excellent chewing texture and is disintegratable and biodegradable comprising biodegradable ingredients, including a lactic acid polymer comprising a poly-L-lactic acid polymer and/or other lactic acid polymers having a glass transition temperature higher than 50° C. in an amount of from 5% by weight to 60% by weight, and an emulsifying plasticizer in an amount of from 1% by weight to 20% by weight. The weight average molecular weight of the lactic acid polymer to be used is preferably 50,000 to 200,000.