A tandem diecasting machine (10) for processing fusible metals comprises a closing unit (12) arranged on the machine frame which accommodates horizontally spaced two diecasting moulds (16; 18). Each diecasting mould comprises two half-moulds (16a, 16b; 18a, 18b) separated in a vertical plane. One half-mould (16a, 18a) of each pair is connected to the closing unit and the other half-moulds (16b; 18b) can slide horizontally in opposite directions, which enables the diecasting moulds to be opened and closed. The machine also comprises an injection unit (14) in which the metal to be processed is stored in the molten state. The metal can be fed in metered quantities by an injection cylinder to a nozzle (36) which can be connected to the closed diecasting mould (16; 18). The inlet channel of the diecasting moulds (16; 18) is arranged on the interface between the half-moulds, and the entire closing unit (17) can be moved horizontally in the longitudinal direction between two terminal positions in which the interface of the two half-moulds in a diecasting mould (16 or 18) is aligned with the nozzle (36) of the injection unit (14). The closing unit (12) and the injection unit (14) can move relative to each other, transversally or longitudinally, between one terminal position in which the injection nozzle (36) is pressed hermetically against the inlet channel of one of the diecasting moulds (16 or 18) and a second terminal position in which the nozzle (36) is separated transversally from the diecasting moulds (16; 18).