Attention is currently being paid to the saccade-related electroencephalogram (saccadic EEG) signal to investigate the brain function in saccadic eye movement. The saccadic EEG has researched to achieve a brain computer interface (BCI) based on intention to eye movement. The spike EEG just before eye movements has been confirmed as the characteristic of saccadic EEG. However, other features have not been reported. In this paper, we focus on a slow cortical potential before a saccadic eye movement. Results show the possibility that the slow cortical potential is related to the bereitschafts potential (BP) of saccadic eye movement.