A comfortable man-machine interfaces are required for current advanced systems. This paper aims at investigating the relation between reaction force of keyboard switches and human switch operation feeling.We investigate how each reaction force of switches effects to the touch feeling of keyboard switches via sensory test.The results of factor analysis for the questionnaire data obtained in the sensory test show that the most substantial factor is the feeling expressed by the words NClearn, "Smooth", "Stiff, and '(Clicking". Finally, each feeling described by each word is directly evaluated by reaction force or vice versa on dual scales. The dual scale for reaction forces and degree of feeling can be directly used for designing comfortable keyboard switch.