PROBLEM TO BE SOLVED : To provide an objective and quantitative risk analysis method of layout in manufacturing facility capable of achieving a well-balanced design between the risk and the cost. SOLUTION : The risk analysis method of a layout in a manufacturing facility includes the steps of : defining the importance of each chamber constituting the layout in manufacturing facility; giving a piece of information 101 on the target facility to be input to a room dust simulator 102; calculating changes of dust concentration in each chamber constituting the layout in manufacturing facility; calculating the occurrence frequency on the basis of the calculation result 103; and determining the risk level in each chamber on the basis of the importance of each chamber previously defined by a risk level determination part 104 and the calculated occurrence frequency. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT