A device for synthesising core-shell nanoparticles by laser pyrolysis is provided. The device includes a reactor having a first chamber for synthesising the core, which is provided with an inlet for a core precursor; a second chamber for synthesising the shell, which is provided with an inlet for a shell precursor; and at least one communication channel between the two chambers for transmitting the core of the nanoparticles to be formed in the first chamber towards the second chamber. The device also includes an optical device for illuminating each of the two chambers, and at least one laser capable of emitting a laser beam intended to interact with the precursors in order to form the core and the shell.