To provide a thermally initiative thermosetting adhesive that needs no additional carrier for the polymerization initiator, solves the problems on the homogeneous mixing, has good storage stability and high reactivity, consequently gives the final product that is uniformly cured and has excellent mechanical strength.

The heat-triggered curable adhesive including at least two kinds of components comprises at least one of polymerizable monomer and/or at least one of a curable resin, polymerization initiators for at least one of polymerizable monomer and/or a curable resin and at least one of filler, when necessary. The polymerization initiator comprises an ammonium salt obtained by organically substituting at least one of the adhesive components and at least inorganic persulfate of the other adhesive component. When they are mixed, an organically substituted ammonium persulfate is formed in situ. The kinds and the amounts of organically substituted ammonium salts, inorganic persulfate, polymerizable monomer and curable resin are selected so that the thermally radical-polymerizable adhesive may be formed.