This paper describes vibration phenomena for stiffened elastic panels having viscoelastic damping layer. The panels are stiffened by beads. The laminated panels are modeled using three-dimensional finite elements in consideration with complex modulus of elasticity. Further, applying asymototic method to the discreted equations of motion, explicit expressions of modal loss factors for the laminates are derived. Consequently, the expressions have similar form to Modal Strain Energy Method, which is proposed by Jonson. Numerical code is developed related to the expressions. Vibration damping properties of the bead panels, which are calculated by the code, is consistent with experimental results. Temperature dependence of the damping properties by FEM also agreed well with the experiments. These investigations reveal that modal damping decreases due to beads of the panels.