A polylactic acid-type polyester resin which fulfills the requirements represented by formulae (1), (2) and (3), has such a self-emulsifying function that an aqueous emulsion of the resin can be produced without using any emulsifying agent or any organic solvent, and has a high biomass level; an aqueous dispersion, an aqueous resin composition, an aqueous adhesive agent, an aqueous coating agent and an aqueous ink, each of which contains the polyester resin; a laminate formed from an aqueous adhesive agent/an aqueous ink; a packaging material; a sustained-release biodegradable covering agent; and a sustained-release biodegradable covering material which is produced from a sustained-release biodegradable covering agent. 1 <= Log(MV) <= 4 ···(1) 300 <= (AV) <= 2,500 ···(2) Log(MV) <= 0.0028×(AV)+1.2 ···(3) In the formulae, MV represents the melt viscosity (Pa·s) of the resin at 80°C; and AV represents the carboxyl group acid value (eq/t) in the resin.
