An electronic keyboard musical instrument comprising: a body unit of the musical instrument; and a stand attached to the body unit; the stand comprising a pair of side boards (18, 20) disposed in a standing manner so as to interpose the body unit therebetween, the body unit comprising a pair of lateral surfaces, each of the pair of lateral surfaces facing one of the pair of side boards (18, 20) and comprising a first engaging portion (30, 32) disposed thereon, each of the pair of side boards (18, 20) comprising a first engaged portion (24, 26) engaged by the first engaging portion (30, 32) and disposed on an inner lateral surface (18a, 20a) thereof, which faces one of the pair of lateral surfaces of the body unit, the first engaging portion (30, 32) and the first engaged portion (24, 26) being engaged with each other by at least one of the body unit and the stand being moved in a predetermined horizontal direction, wherein the first engaged portion (24, 26) is a guide groove formed so as to extend in the horizontal predetermined direction, one of the body unit and the pair of side boards (18, 20) is provided with projections protruding in a standing direction of the pair of side boards (18, 20), and another is provided with restriction grooves adopted such that the projections are engaged therewith, each of the projections is engaged with one of the restriction grooves, when the first engaging portion (30, 32) is engaged with the guide groove (24, 26), the first engaging portion (30, 32) is a protruding portion protruding from each of the pair of lateral surfaces of the body unit, characterized in that each of the restriction grooves is disposed inside of the guide groove (24, 26), and each of the projections is disposed on the protruding portion (30, 32). a body unit of the musical instrument; and a stand attached to the body unit; the stand comprising a pair of side boards (18, 20) disposed in a standing manner so as to interpose the body unit therebetween, the body unit comprising a pair of lateral surfaces, each of the pair of lateral surfaces facing one of the pair of side boards (18, 20) and comprising a first engaging portion (30, 32) disposed thereon, each of the pair of side boards (18, 20) comprising a first engaged portion (24, 26) engaged by the first engaging portion (30, 32) and disposed on an inner lateral surface (18a, 20a) thereof, which faces one of the pair of lateral surfaces of the body unit, the first engaging portion (30, 32) and the first engaged portion (24, 26) being engaged with each other by at least one of the body unit and the stand being moved in a predetermined horizontal direction, wherein the first engaged portion (24, 26) is a guide groove formed so as to extend in the horizontal predetermined direction, one of the body unit and the pair of side boards (18, 20) is provided with projections protruding in a standing direction of the pair of side boards (18, 20), and another is provided with restriction grooves adopted such that the projections are engaged therewith, each of the projections is engaged with one of the restriction grooves, when the first engaging portion (30, 32) is engaged with the guide groove (24, 26), the first engaging portion (30, 32) is a protruding portion protruding from each of the pair of lateral surfaces of the body unit, characterized in that each of the restriction grooves is disposed inside of the guide groove (24, 26), and each of the projections is disposed on the protruding portion (30, 32).