The purpose of this study is to examine the relationship between the structural characteristics (intensity of a norm, range of tolerable behavior and potential return difference) of the group norms regarding improvement proposals, psychological safety and occupational stress among engineers working in the information and communication industry. A survey by the web-based method was conducted with 602 Japanese employees (601 valid responses). Therefore, a 2-1-1 multilevel mediation analysis using a hierarchical linear model was calculated to confirm that psychological safety could be a mediator of the correlation between structural characteristics (intensity of a norm, range of tolerable behavior and potential return difference) and occupational stress, the data hierarchy of each job type was recognized by calculating ICC. The results showed that psychological safety had a mediating role in the relationship of intensity and potential return difference of the norm and stress responses.