We performed spectral measurements of gas discharge luminescence caused by triboelectricity during sliding friction between a diamond spherical surface and a quartz plate in N-2. As the gas pressure decreased, luminescence of negative glow intensely appeared and vibrational temperature of electronic excited N-2 increased. The spatially resolved spectral measurements made it clear that the spectrum of N-2 discharge differs from position to position; emission from negative glow was relatively strong on the frictional track where is far from the contact. This result implies that the diamond tip was charged to positive and the frictional track on the quartz to negative. (C) 2004 Published by Elsevier B.V.