A plane-type speaker where, on one of the main surfaces of an exciter film, there are placed piezoelectric films which are expanded and contracted by sound-releasing driving signals applied thereto. An oscillation plate is secured to the excited film through frame members. The oscillation plate has a flat-plate shape and is secured to the exciter film while having a warped shape such that it is gradually spaced further away from the exciter film, with decreasing distance from the secured ends to a center area, when viewed at a side surface. This realizes a state where the exciter film is pulled outwardly with respect to the secured ends due to bending stresses therein. If sound-releasing driving signals are applied to the piezoelectric films in this state, the exciter film contracts and expands along with the expansion and contraction of the piezoelectric films, thereby causing the oscillation plate to oscillate.