Low-velocity impact on composite sandwich panels has been investigated. The contact force is computed from a proposed modified Hertzian contact law. In the proposed contact law, the exponent is adjusted and the through-the-thickness elastic constant of honeycomb core is reduced properly to approximately predict the measured contact force-time history during the impact. The equivalent transverse elastic constant is calculated from the rule of mixture. Nonlinear equation to calculate the contact force is solved by the Newton-Raphson method and time integration is done by the Newmark-beta method. A finite element program for the low-velocity impact analysis is coded by implementing these techniques and an 18-node assumed strain solid element. Behaviors of composite sandwich panels subjected to low-velocity impact are analyzed for various cases with different geometry and lay-ups. It has been found that the present code with the proposed contact law can predict measured contact forces and contact times for most cases within reasonable error bounds, especially for thick sandwich plates.