Disclosed are an ultrasonic diagnostic instrument, and an arm-assisting device (3) for the ultrasonic diagnostic instrument. The ultrasonic diagnostic instrument comprises a display, a control panel, an ultrasonic host, a probe and the arm-assisting device (3), wherein the arm-assisting device (3) comprises a stand (3100) for being mounted to other objects or being stood on the ground, an arm rest (3200) for supporting an arm of a user, and a cantilever (3300), with the cantilever (3300) connecting the arm rest (3200) to the stand (3100) to separate the arm rest (3200) from the stand (3100). When medical care personnel use the probe for scanning, the medical care personnel can place an arm on the arm rest (3200), such that a burden on the arm of the medical care personnel is reduced by means of a support effect of the arm rest (3200) on the arm of the medical care personnel, thereby reducing the probability of medical care personnel suffering from an "occupational disease" such as arm soreness and arthralgia. Because the cantilever (3300) separates the arm rest (3200) from the stand (3100), the possibility of the stand (3100) hindering arm movements of the medical care personnel is reduced, thus facilitating the arm of the medical care personnel in flexibly moving on the arm rest (3200).L'invention concerne un instrument de diagnostic ultrasonore, et un dispositif d'assistance au bras (3) pour l'instrument de diagnostic ultrasonore. L'instrument de diagnostic ultrasonore comprend un dispositif d'affichage, un panneau de commande, un hôte ultrasonore, une sonde et le dispositif d'assistance au bras (3), le dispositif d'assistance au bras (3) comprenant un support (3100) destiné à être monté sur d'autres objets ou à être debout sur le sol, un repose-bras (3200) pour supporter un bras d'un utilisateur, et un porte-à-faux (3300), le porte-à-faux (3300) reliant le support de bras (3200) au support (3100) pour séparer le repose-bras (3200) du support (3100). Lorsque le pe
