In the past, several investigations have been made on the vibrational characteristics of finite length sandwich beams with a viscoelastic core between two elastic layers. Since the viscoelastic core is not usually joined perfectly to the elastic layers with adhesive and is not thick enough in comparison with adhesive layers, it is considered that the adhesive layers have a great effect on vibrational characteristics of the sandwich beams. Nevertheless the effect of adhesive bonding has been neglected in the existing theories1)3)∼5).The purpose of this paper is to elucidate the effect of adhesive bonding on damping characteristics of the sandwich beams. The sandwich beams were assumed to consist of two elastic layers, one viscoelastic layer and two adhesive layers in the present analysis. Moreover, properties of the adhesive were assumed to vary from the original depending on the condition of adhesive bonding. Many specimens were made and tested to verify the theoretical solutions. The experimental results agreed well with the theoretical ones and showed that the effect of adhesive bonding could not be neglected. Thus, the effect of adhesive bonding should be taken into account when the sandwich beams are designed. The degree of the effect of adhesive bonding was qualitatively expressed by using the non-dimentional parameter A*.