To provide a thickening agent and a thickening composition having high thickening properties, excellent feeling of use without stringiness and good biodegradability without a fear of adverse effects by a residual solvent.

This microgel useful as the thickening agent is obtained by dispersing an aqueous solution or an aqueous dispersion of one or more kinds of polysaccharides having a gelation ability in an oily phase containing one or more kinds of lipophilic surfactants and making an inner aqueous phase of the resultant water-in-oil type emulsion gel. The thickening composition is obtained by depositing the resultant microgel in an organic solvent, recovering the deposited microgel and dispersing the recovered microgel in an aqueous carrier.