PURPOSE: To provide a forming method for a cable connecting part, obtainable an excellent electric characteristic appliable to even a super-high-voltage cable exceeding 275kV, e.g. 500kV, and moreover excellent in workability having a short working time.

CONSTITUTION: A conductor 12 is connected by a compressed sleeve 13, then a heat contracted tube, composed of fluoreresin and being astride a cable insulating body 14, is mounted on the outer periphery of the conductor 12, and the surface of the cable insulating body 14 is heated from above at a temperature of e.g. 400°C or more to form a polyethylene layer 15 of non-bridge-formation or a low-bridge-formation degree on the surface layer part of the cable insulating body 14. Then the heat contracted tube is removed, a split die for forming a reinforcement insulating body is coveredly engaged on a conductor connecting part with the cable insulating body 14 strided, and heat-melted super-low-density polyethylene, having e.g. a melting point of 116°C and a density of 0.890, is pressed in and hardened to form a reinforcement insulating body 16 composed of non-bridged polyethylene.