An electronic keyboard musical instrument, including: a housing having a lower casing having a bottom wall and an upper casing having a top wall, left and right walls being formed on at least one of the top wall and the bottom wall; a keyboard portion held by the housing; at least one speaker disposed at at least one end portion of the housing in its key arrangement direction, such that its sound emission surface faces rearward; a sound adjuster disposed in the housing so as to be located outward of the speaker in the left-right direction; and a plurality of protruding portions formed at the one end portion so as to protrude from the at least one of the top and bottom walls, wherein the sound adjuster is held by at least one of the protruding portions.