Abstract: A polyvinyl acetal/polyester graft copolymer obtained from a polyvinyl acetal having one or more of each of constituent units represented by the following general formulae (1) to (3) (wherein each of R1 and R2 represents a hydrogen atom, a linear or branched alkyl group having a carbon number of from 1 to 20, or an aryl group, in which the alkyl group or the aryl group may have a substituent) and having a weight average molecular weight of from 100 to 100,000 is used as a dispersant which prevents aggregation of solid particles in a dispersion liquid from occurring, is effective for forming a stable dispersion liquid, and exhibits excellent heat resistance.