Jahn-Teller distortion in C-60(-) ion has been studied by C-13 nuclear magnetic resonance spectroscopy in the solid samples KC60(THF) and KC60(THF)(x)(0 < x < 1). Solvating K+ ion by THF can change electronic states of C-60(-) ion. When C-60(-) is less affected by K+ ion, the ground state is a (2)A state, which is in good agreement with the ab initio calculation for the free C-60(-) ion. When C-60(-) is perturbed strongly by K+ ion, however, the ordering is inverted, leading to the more stable E-2 state.