An electronic keyboard musical instrument, including: an instrument main body; a keyboard portion including a plurality of keys as performance operating elements; a musical-sound-signal generating portion configured to generate a musical sound signal by a key operation of the keyboard portion; and at least one planar speaker configured to output a sound in accordance with the musical sound signal generated by the musical-sound-signal generating portion, wherein the planar speaker is formed by superposing a plurality of flexible layers that at least include a vibrating layer and electrode layers which sandwich the vibrating layer from opposite sides of the vibrating layer and wherein the planar speaker is disposed at an inside of a casing that constitutes the instrument main body or disposed at a portion of a surface of the casing.