The eye fixation related potential (EFRP) associated with the occurrence of fixation pauses can be obtained by averaging EEGs at termination of saccades. EFRP is a kind of ERP measurable at the eye movement situation. Variations of EFRP were examined during a proof reading task for a long time. Two paragraphs of sentences were presented on the left and the right sides of a CRT. The paragraph on one side had some irrelevant words. Ten subjects were asked to detect the irrelevant words. The task started at 09.20 h and finished at 16.00 h and consisted of five blocks. The duration of each block was 1-h task and 10-min rest including a lunch (70 min). EEG and EOG were recorded during the task. EEGs were averaged at termination of saccades to obtain EFRP. EFRP showed little changes during the morning blocks. However, the mean amplitude between 100 and 200 ms of the positive component in the last two blocks decreased significantly compared with other blocks. The error rate, the performance and the score of fatigue increased at the end of the task. EFRP would reflect decline of mental concentration (i.e. carelessness) caused by visual fatigue.