This study deals with noise occurring in the process of human information transmission. Human process many kinds of information by receiving them from the outside or using their own thought and express the processed information to the outside by acting. In this process, Channel Noise (C_N) is defined as the characteristics of noise generating the incomplete result for the external stimulus. To evaluate C_N, keyboard-typing experiment has been performed to the 87 subjects. In this experiment, the subject consists of college students who have abundant experience in computer usage. In the experiment, there were some cases that typing order was unconsciously reversed. In this study, we deal with only these cases since these cases can be used as important data to study humans information transmission system.