In an assembly of an electronic device having one side provided with at least one securing hole, and a securing device including a body, an abutting and retaining member, and a guiding unit, the body includes a base for placement of the electronic device thereon, and a lateral plate extending upwardly from one side of the base and having an inner side formed with at least one protrusion for engaging the securing hole. The abutting and retaining member is movably and slidably disposed on the base opposite to the lateral plate. The guiding unit is connected to the abutting and retaining member and the base for guiding displacement of the abutting and retaining member so that the latter is rotatable relative to the base to abut against the other side of the electronic device when being displaced from a release position to a securing position.