This museum showcase comprises a load-bearing frame comprising tubular beams with quadrangular section connected together by at least one joint, and is characterized in that the joint comprises two flat and parallel plates, wherein each plate comprises a middle portion and at least two attachment wings, wherein the two attachment wings of each plate are respectively inserted in a first and a second of the tubular beams and fixed to them. In this way, the showcase can be designed and built in a particularly quick and easy manner. Both the beams and the joints can be made starting from extremely simple and cost-effective semi-finished products (tubes and plates, respectively), with elementary processes, basically simple cuts to the desired sizes.