In recent years, accident induced by human error is increasing in the chemical plant. Human error analysis of the chemical plant was conducted on the basis of past accident. Some company called by A for the basis of a chemical accident. Factor analysis of human errors was separated in plant operation and work. Agency's work of occupational safety & health was classified into four types. It is based on the work before, during work, recovery work, and discontinue work. It was still separated work of human error by analysis and then was derived factor and issue. The human error factor and priority for accident prevention in the chemical plant is presented.