Human factors in ship operation include interfaces between an operator and physical or nonphysical elements that adjacent to him/her ; such as navigation instruments, regulations, ambient environmental conditions, and those who are involved in the operation. Human factors research is required to provide a method to express how personnel on site consider the working conditions affect them with their performance, what they require to be changed or adjusted, and what they perceive as top priority for safe navigations. In this paper, we propose a human factor model extended from m-SHEL model to classify ship operation's human factors. Our model provides practical definitions to each interface of the m-SHEL model according to actual ship operations, especially pertaining to the factors relating to collision and grounding avoidance, along with tree-structured subcategories that provide the detailed representation of the interface. Considering the human factors relate to the two kinds of situation, we defined 53 subcategories in all. Then seafarers' comments on top priority for each situation, which are retrieved from questionnaire survey, are classified. The analysis and discussion upon the classified comments data show reasonable relations between seafarer's attitudes and their occupational attributes or ship types.