[en] The importance to make use of lessons learned and knowledge from accidents and troubles in safety management of nuclear research facilities is recognized widely. By the root cause analysis of accidents and troubles, lessons learned and knowledge have been arrived about safety management of facilities. The root cause analysis has been performed for accidents and troubles generated at nuclear research facilities in Japan Atomic Energy Agency (JAEA) from about 1990. Because the analysis is performed for various facilities, anyone have been used the analysis method of possible of utilize. On this account the analysis method has been developed and adopted an existing analysis method. This report introduces the analysis method that has been used for the root cause analysis of these accidents and troubles. Furthermore, this report apply a generally well known JCO Criticality Accident to each analysis method as an example and explain on the direction for uses. (author)