Nuclear magnetic resonance under high pressure (3.0 GPa at room temperatures) were performed in a spin ladder system, Sr2Ca12Cu24O41 where the superconductivity is realized by applying pressure above 3 GPa at low temperatures. The relaxation rate 1/T-1 on Cu-63 nuclei shows an activated behavior at high temperatures above 50 K although the system is metallic, and the value of the excitation gap is almost the same with that at ambient pressure. The fact implies breakdown of a scenario that pressure vanishes the spin gap and then superconductivity is induced. (C) 2003 Elsevier Science B.V. All rights reserved.