Provided is an aqueous composition containing alginic acid or a derivative thereof, the composition having a viscosity retained stably over a long period of time. The alginic acid-containing aqueous composition includes alginic acid or a derivative thereof (A), water (B), and a non-reducing sugar (C). Also provided are a dental alginate impression material and a base material for a dental alginate impression material each using the composition, in which the viscosity of the aqueous composition is stably maintained for a long period.
