A carboxymethylmannoglucan comprising tetrasaccharide units represented by the following general formula (I) and salt thereof. Further, the invention discloses a carboxymethylmannoglucan derivative and salt thereof produced by subjecting part or the whole of mannose of the tetrasaccharide units to ring opening and subjecting part or the whole of glucose which constitute the main chain but have no mannose as a branch <IMAGE> (I) wherein R1 to R12 each represent a hydrogen atom or a carboxymethyl group. The compounds are useful as carrier for delaying the disappearance of a drug in the blood and for enhancing the organotropism of the drug for a carcinoma.
