An aluminum chelate-based latent curing agent for curing a thermosetting epoxy resin, wherein an aluminum chelate-based curing agent interfacially polymerizes a polyfunctional isocyanate compound and, at the same time, is held in a porous resin obtained by radically polymerizing a radical polymerizable compound in the presence of a radical polymerization initiator, the surface of said aluminum chelate-based latent curing agent having been subjected to an inactivation treatment with an alkoxysilane coupling agent. As the alkoxysilane coupling agent, an alkylalkoxysilane is preferred. The radical polymerizable compound preferably comprises a polyfunctional radical polymerizable compound.