To provide a heat resistant dispersant having enough hot water resistance and hydrolysis resistance, capable of keeping a stable viscosity with small viscosity reduction under the condition of a high temperature and a salt- water and capable of being utilized for application to a mud water conditioner for excavating, a polymer for recovering a crude oil, an agent used for fiber, the agent used for civil engineering work, a polymer flocculant or the like.

The heat resistant dispersant contains a (co) polymer using hydroxyethyl (meta) acrylamide, preferably hydroxyethyl (meta) acrylamide of 5 to 100 wt.%, separately or together with other copolymerizable vinyl monomers.