A thermoset adhesive for bonding two materials having different linear expansion coefficients with reduced warping and without spaces being formed therebetween. The thermoset adhesive of the present invention comprises an epoxy resin, a core-shell rubber, thermally expansive microparticles, and a curing agent. The thermally expansive microparticles can have at least one or any combination of an average particle size of from 9 to 19 μm, an expansion initiation temperature of from 70 to 100° C., and a maximum expansion temperature of from 110 to 135° C.