An amphiphilic compound having a dendritic branch structure represented by general formula (I): ##STR1##

In the formula (I), R₀ is a hydrophilic group; R₁ and R₂ are independently a hydrophobic group; and n is an integer of 1 to 4. This amphiphilic compound is capable of stably fixing a water-soluble polymer onto a surface structure by taking advantage of intermolecular interaction, thereby enabling the water-soluble polymer to be carried thereon without giving any damage to the function thereof.