As opposed to rigid-body mechanisms, the structural elements of a compliant mechanism utilizes their elastic characteristic to generate a specifying mobility on the predetermined portion, or to delivers the desired motion and force by undergoing elastic deformation. Even the mechanical structure is designed and built as a rigid one, often the entire structure has a compliant comportment resulting from elastic deformations of links, elasticity of joints, dumping elements etc. Numerical simulation of mechanical response of such structure can be formulated using finite element method. In this paper a method to determine dynamical response of a compliant planar mechanism is proposed.