This paper verified the characteristics of electrical continuity and mechanical strength of steelwork required to use it as a down-conductor in lightning protection system. It was proven that the steelwork in reinforced concrete apartment has an excellent electrical continuity with low resistance(less than 0.2[${Omega}$].). But it was confirmed that a poor connection between two reinforcement bars can easily cause serious damages of the concrete even with the impulsive current of 50[kA], 10/350[${mu}s$]. These results of experiments mean that the additional measures are necessary in using the steelwork as the down-conductor of the lightning protection system.