To provide a tatami core for a thin tatami using a vacuum insulation material which is thin in thickness and excellent in rigidity and insulation property, in which the periphery of the tatami core can be cut and allows a needle to be used there, and preventing its vacuum sealing from being impaired due to a hole in the vacuum insulation material, without using a special machining method in a process of producing the tatami from the tatami core.

A tatami core is constituted by a tatami backing side cushion layer, a core layer, a rigidity maintaining layer and a tatami surface side cushion layer, where a vacuum insulation material and an outer peripheral core layer which is disposed on the outer side periphery of the vacuum insulation material and can be cut are used for the core layer of the tatami core.