In the present invention, a hydraulic binder is rapidly cured using either: (1) a liquid quick-setting agent for a hydraulic binder, comprising aluminum sulfate or a hydrate thereof, an aluminum oxide or hydroxide, at least one organic acid, at least one alkaline earth metal oxide or hydroxide, and water; or (2) a combination of (A) a liquid quick-setting agent which contains aluminum sulfate or a hydrate thereof, an aluminum oxide or hydroxide, at least one organic acid, at least one alkaline earth metal oxide or hydroxide, and water; with (B) a non-slurry auxiliary quick-setting agent which contains powdery aluminum sulfate or a hydrate thereof. In accordance with the present invention, a quick-setting agent system which is easy to use, produces little dust, is non-alkaline, and is capable of exhibiting good curing properties even under conditions which are difficult to carry out construction with conventional quick-set concrete.