Tonsillectomy is the one of operation that is performed the most commonly in otolaryngology field. Many changes that include range of voice, tone, voice quality and resonance were made by tonsillectomy. Sometimes, any patients taken tonsillectomy has suffer from these voice problem after tonsillectomy. However there are less study for these problems until now. Then, we studied to find the anatomical findings that affected the voice quality when tonsillectomy was performed. We evaluated the voice in 2 groups, one is the group showed the normal pharyngeal space by using the transnasal fiberscopy, the other is group showed medially bulging tonsil at pharyngeal cavity by using same method, with perceptual evaluation, nasalance score, nasality, oral formant and nasal formant. We used the computerized speech analysis system, the nasometer and the spectrogram in the CSL program. We could not find any differences in perceptual evaluation between two groups. But objective measures were provided. Nasalance score and nasality on the nasometric analysis were increased significantly and oral formant on the spectrogram was changed singnificantly after tonsillectomy in Group 2. Authors thought medially bulging tonsil in the pharynx is able to affect the voice quality after tonsillectomy when we evaluted through the nasal cavity by the using of fiberscopy and this evaluation would be important especially in singers.