Abstract: An apparatus (1) for molding and assembling a chamber unit (D) for biomedical use comprising two plates (18, 22), which are mutually parallel and opposite and are allowed to move toward and away from each other, for supporting the mold parts of a first forming mold (3) and of a second forming mold (4) for the injection molding of thermoplastic material respectively of two parts (A, B) of a chamber unit (D) that are adapted to be mutually assembled, and the mold parts of a mold (5) for the assembly, by overmolding additional thermoplastic material, of the two parts (A, B), an element supporting device (6) that is rendered movable between the plates (18, 22) by actuation means (M) and is adapted to receive the parts (A, B) from the first (3) and second (4) forming molds and to transfer them to the assembly mold (5); the element supporting device (6) is directly associated, at least slidingly, with at least one of the supporting plates (18, 22).