To provide a flat panel speaker having a piezo-electric actuator to reduce stress developed and concentrated at the root of a piezo-electric ceramic vibration cone to a cross-sectional U-shaped electrode holder.

At the flat panel speaker, a piezo-electric actuator 10 holds a plate type piezo-electric ceramic element 14, and a piezo-electric ceramic vibration cone 11 composed of an electrode foil disposed at one plane of the cone and an electrode thin plate 13 disposed at another plane of the cone using a cross-sectional U-shaped electrode holder 21. The center of the piezo-electric ceramic vibration cone 11 is laminated, engaged and fixed in a gap formed with a top holding plate 211 and the bottom holding plate 212 of the electrode holder 21, together with a stress distribution plate 30. The stress distribution plate 30 is attached to a stress concentrated section at both roots of piezo-electric ceramic vibration cone 11 to the electrode holder 21 in an extended and projected fashion. The plate is configured with a metal plate or a synthetic resin plate having rigid elasticity for transforming in response to vibration by the piezo-electric ceramic vibration cone 11.