Eye mouse is an input device which uses a person`s gaze and eye movements as input to operate a mouse cursor by using the eye tracking technology. Eye mouse is an input device which can reflect cognitive intentions of a user immediately from a user`s eye(s). In this study, the functions of eye mouse, such as click, double-click, drag and scroll, was investigated and evaluated by supposing real computer interaction situation. In this study, usability of the different operation methods of eye mouse which correspond to the functions of conventional mouse was investigated and evaluated. The experimental result showed that there was performance difference between the different operation methods of eye mouse. The questionnaire result also showed that there was satisfaction difference between the different operation methods of eye mouse. The result of this study made us know what is the pros and cons about usability on the use of eye mouse. The result of this study can help to comprehend interfaces for eye mouse, and can contribute to the establishment of guidelines for development in interface design and operation methods for eye mouse.