The purpose of this study is "Development of tatami mats considering sound insulation performance and safety and formulation of floor structure design guidelines". This paper reports the results of two studies, one of which is a survey on sound insulation performance. As a result of the survey, the most frequently pointed out sources of "sounds heard and noticed" were "footsteps from upper floors", "children jumping and running around", "falling objects", and "moving chairs and furniture", as well as floor impact sound. Thus, it was confirmed that the sound insulation property of the floor is an important item. The other is a proposal for tatami floors that takes sound insulation and safety into consideration. As a result of the study, some of the tatami floors showed a reduction of 3 to 4 dB in floor impact sound level in the 63-Hz band. In addition, the maximum values of acceleration G (head model) of the prototypes were small, ranging from 20 to 32 G. These results suggest that several types of tatami floors can be developed with sound insulation and safety.