Epoxy thermoset materials are applied to a number of industrial products as a matrix of adhesive, and they are driving the technical progression of light weight organic-inorganic composite equipment. The precise design of materials is important in order to satisfy the required properties according to the intended use. For such material design, the further application of new analytical techniques enables the evaluation of functionality and stability with high accuracy, which up to now has been considered to be difficult to achieve. In the present study the reactivity of a small amount of epoxy thermosetting resin and molecular mobility in the adhesive film for semiconductor were evaluated by 1 H Pulse NMR. They were found to differ according to the molecular weight of acrylic copolymer present but could not be confirmed using the conventional evaluation method. Comparing adhesive properties, heat treatment before curing greatly affected the adhesion property but there was no effect with less reactive adhesive film. Additionally, it is suggested that this reactivity is due to the molecular mobility and it depends on the molecular weight of the acrylic component.