The gel composition according to the present invention comprises an amphiphilic block polymer that comprises a hydrophilic block chain having 20 or more sarcosine units and a hydrophobic block chain having 10 or more lactate units. The gel composition of the present invention has an excellent sustained releasability of a water-soluble drug, etc. and places a reduced burden on the living body. The gel composition may be provided in the form of an organogel, hydrogel or xerogel. A xerogel can be obtained by removing a dispersion medium from an organogel. A hydrogel can be obtained by wetting a xerogel with water or an aqueous solution.
