A part-holding device in a method for repairing a blade of a monobloc bladed disc of a turbo-machine, through electron-beam welding of a patch onto the blade along a junction plane is disclosed. The device includes a disc supporting device which supports the disc and an adjustable holding device which holds the blade and the patch. The adjustable holding device includes a platen which supports the adjustable holding device, arranged such that the space located above the junction plane allows for an electron beam to pass. The relative positions of the blade and the patch are set using the adjustable holding device that is supported by the platen, while leaving some space allowing for an electron beam to pass. Such a device is simple and reliable.