The purpose of this study is to examine how human errors which cause labor accidents occur and how they can be reduced to a minimum. In this study,two labor accidents caused by human errors were dealt with as case studies,in which we conducted semi-structured interviews with sixteen employees of a manufacturing company including victims,coworkers,maintenance workers,supervisors and managers. This study clearly states problems of the organization: maintenance delay of unstable facilities,managers’ ignorance of employees’ requests,attachment of importance to productivity,difficulty of evaluation of safety activities,and management of production line in a haphazard way. The result indicates what top executives,managers and supervisors should do to prevent human errors.