There are some types of beds. Some mattresses with a barometer of amenity are provided for customers by means of sensory expression. However, the mattress is a structure with complicated structural characteristics. And those structural characteristics could affect human sense, when the customer is on a mattress. The aim of this study is to show an index of mattress from the viewpoint of the engineering by focusing the structural characteristics that especially could affect judgmental bases for choosing mattress. This study was approached from three points that were the calculation of the vibration model in mechanical engineering, the questionnaire survey in the kansei engineering and the experiment by the electromyogram in the biological engineering. From these results, when structural characteristics between mattresses are different, sensory characteristics and biological characteristics are also different. Therefore, it is possible to suggest the index of mattress by considering structural characteristic of the mattress.