A leg/elbow fixing device including a support bar having two connecting sections and two bracket assemblies fixable on the leg or elbow of a user. The bracket assemblies are adjustably located on the connecting sections of the support bar. Each bracket assembly includes a locating mechanism having a cavity in which the connecting section of the support bar is fitted. A receptacle is formed on top face of the cavity. A locating assembly is received in the receptacle. Each connecting section of the support bar is formed with notches. The locating assembly includes two arresting members each having a projecting block engaged with any of the notches of the support bar. The locating assembly further includes a restoring member compressed between the arresting members and a stop section. The stop section includes an upper cover and a cover member. The cover member is fixed in the receptacle for preventing the arresting members and restoring member from bounding out. The upper cover has two engaging blocks locked in the restricting holes of the arresting members for locating the bracket assemblies on the support bar.