To obtain a tatami mat which is light-weight and excellent in fireproof property and whose tatami bed can be easily cut and sewed and further whose warf can be prevented by providing a reinforcing material made of a foamed body of polypropylene or polyethylene and a sheet and a core material having a noncombustible or frame-retardant characteristic.

The expansion ratio of foamed bodies 5, 7 such as polypropylene or polyethylene is 1.1-6 times. The tatami mat has a tatami bed 2 of 21-60 mm in the whole thickness. In this case, when the foamed bodies 5, 7 relative to the upper and lower faces of the core material are used as reinforcing materials, the expansion ratio of the upper foamed body 5 is made 2-4 times and that of the lower foamed body 7 is made 1.2-4 times. In this time, the thickness of the reinforcing material of the upper foamed body 5 is made 2-6 mm and that of the lower foamed body 7 is made 1-4 mm. When using it for a thin tatami bed 2, the whole thickness is made to be not more than 20 mm and the thickness of the reinforcing material of the upper foamed body 5 is made 1-4 mm and that of the lower foamed body 7 is made 0.5-2 mm. In this way, a tatami mat chiefly made of a resin which is excellent in heat insulation property and prevents dust from stirring up can be obtained and the working environment can be improved thereby.