In this paper, a combination of the boundary element method and the finite element method was applied to the stress intensity factor analyses of an interface crack in adhesive joints. The virtual crack extension method was utilized for finite elements allocated around a crack tip to obtain the energy release rate of a crack. The superposition technique proposed by Matos was utilized for the mode separation of the stress intensity factor of the interface crack. We applied the present method not only to a bimaterial plate with a center interface crack, but also to adhesive joints with a center interface crack or a slant interface crack to show the effectiveness of the present method for analyses of an interface crack in a very thin adhesive layer. Furthermore, the fracture toughness of an adhesive joint with an edge crack for various adhesive thicknesses was experimentally determined using the present analytical method. As a result, we obtained a constant fracture toughness regardless of the thickness of the adhesive layer.