PROBLEM TO BE SOLVED: To provide a thermosetting fluoropolyether-based adhesive composition which cures by a heat treatment of less than 100°C, shows the excellent adhesion to metals, an inorganic substance, and a plastic substrate, and is excellent in a bond durability at less than 100°C, and to provide a method for bonding the composition with a metal, inorganic substance, or plastic substrate.SOLUTION: The thermosetting fluoropolyether-based adhesive composition contains (A) a specific linear polyfluoro compound, (B) a silicon atom-bonded hydrogen atom-containing fluorine-containing organohydrogenpolysiloxane, (C) a platinum group metal-based catalyst, (D) a fluorine-containing organohydrogenpolysiloxane that has a fluorine-containing organic group, a silicon atom-bonded hydrogen atom, an epoxy group and/or trialkoxysilyl group that bonds to a silicon atom through a carbon atom or a carbon atom and an oxygen atom, and an aryl group that bonds to a silicon atom through a carbon atom, (E) a specific organosilicon compound, and (F) an organosilicon compound that has an epoxy group and a silicon atom-bonded alkoxy group.