A hot-melt adhesive comprising a self-curing unsaturated polyester resin having an air-drying functional group and an average polymerization degree of 8 or more has been found to have an excellent heat resistance and a high bonding strength when it is bonding-cured under heat and pressure. If an additive selected from a polymerization initiator, a polymerization promotor and a photosensitizer is incorporated into the present air-drying, self-curing polyester resin, the curing speed is extremely increased to such an extent as cannot be expected from the conventional curing type adhesives. The incorporation of such an additive into the self-curing unsaturated polyester resin is advantageously realized in the form of composite structures of various forms, e.g., a laminate form, a core-in-sheath form and an islands-in-sea form. Such a composite hot-melt adhesive structure is useful for improving a pot life. If a thermoplastic polymer is incorporated, the resulting hot-melt adhesive is further improved with respect to bonding strength. Since the present hot-melt adhesive is solvent-free and does not contain as a cross-linking agent a vinyl monomer, it is easy to handle and environmental pollution can be advantageously avoided.