This paper suggests a theoretical method to predict a frequency response function of a connected beam, which consists of two different beams, from frequency response functions of individual beams. For a finite element model of each beam, frequency response functions between all nodes and one identical excitation point are obtained through the harmonic analysis of a commercial finite element program. In order to obtain a receptance matrix of each beam, the experimental modal analysis method is applied to the frequency response functions. Two receptance matrices of two beams are combined into a block matrix, and a compatibility condition is used to obtain a receptance matrix of a connected beam. The frequency response function calculated by using the receptance matrices is compared with that of a connected beam.