To prevent a cavity from forming in the internal space in a corrugated section by covering the core of a power cable with a protective tube containing a primary compound, and then filling the remaining space in the protective tube with a secondary compound.

Cores 14 of power cables 10 to be connected with each other are covered with a protective tube 28 to form a power cable connection 12. Before doing this, a primary compound 30A is formed so that the internal space in a corrugated section 40 of the protective tube 28 is filled with the primary compound. Furthermore, a secondary compound 30B is injected gradually into a remaining space 44 in the protective tube 28 and integrated with the primary compound 30A which is already present in the protecting tube 28, and the protective tube 28 is thereby filled with a compound 30. As a result, a cavity is positively prevented from being formed in the internal space in the corrugated section 40.