The invention relates to a cable fixing device, which comprises an adjustable mounting rack capable of adjusting high, low, front and rear positions of cable fixing clamps and at least one cable fixing clamp which is fixedly arranged on the adjustable mounting rack, wherein each cable fixing clamp comprises a clamping seat used for clamping a cable through a locking device after the alignment of the cable and a clamping cover; clamping through slots for clamping the cable are formed in the clamping seats; hollow cavities are respectively formed in two side walls of the clamping through slots; clamping bulges which can be inserted into the corresponding hollow cavities when the clamping covers and the clamping seats are aligned are arranged on aligned end faces of the clamping covers; and cable clamping surfaces on the clamping bulges and the clamping through slots on the clamping seats form cable clamping space of which the size is changed along with change of the alignment depth of the clamping covers and the clamping seats. By the cable fixing device, the stress of mechanical fastening on the cable can be reduced, the cable mounting reliability is improved, faults of cable heads are reduced, and the same cable fixing clamp can be matched with cables of different wire diameters. The invention also relates to a cable fixing clamp.