To provide a device capable of solving problems such as dew forma tion, harmful insect, the air contamination and smell in a room caused by poor ventilation by high air-tightness of a dwelling house and the poor ventilation from a floor on which a tatami mat is laid, and achieving the health-promoting benefits such as quiet sleep and relaxation by effect of minus ion, and the improvement of life quality.

Charcoal is included in an interlining of a tatami mat in a state of being put in a cassette, and placed in straw of a tatami mat floor by utilizing the porosity as the characteristic of charcoal. By laying the tatami mat, the clarification of air, the adjustment of humidity, the bactericidal action, the prevention of harmful insect, the quiet sleeve by releasing minus ion, and the relaxation effect through charcoal, can be promoted.