Acoustic Emission (AE) is the emission of elastic stress waves resulting from deformation and fracture of materials. The AE signals depend on the intensity of deformation and fracture of materials. A tribological phenomenon is a kind of deformation and fracture occurred at material surfaces. Therefore, it could be possible to observe the tribological phenomena by measuring AE signals. In this paper, we measured AE signals and voltage of contact in dry rubbing. A state of the contact influences tribological phenomena. Accordingly measuring contact voltage makes evaluation of the contact state effective. The AE signals were analyzed by short time Fourier transform. We examined frequency spectrum of the AE signals accompanied by the different shifts of the contact state. In consideration of that, we discussed the relationship between AE signals and tribological phenomena.