Identification device of the k conductivity and / or thermal capacity C of a flat wall, comprising: first and second sensors (Ao, AL) temperature placed on both sides of the wall; a third sensor (A), which can be a temperature sensor positioned adjacent the first face or a heat flux sensor positioned adjacent the first face; of suitable data processing means, from the measurements supplied by said sensors, to determine the conductivity coefficient k and / or the thermal capacity C of the wall. The processing means determine the conductivity coefficient k and / or the heat capacity C, by calculating the temperature change in the wall during a time interval, in particular from the measurements provided by the third sensor. ; The values ​​used for the conductivity coefficient k and / or the heat capacity C, are those for which, during the said period, the differences between the temperature values ​​([theta] (0, t), [theta] (L, t )) calculated for the first and second faces and the temperatures ([theta] d1 (t), [theta] d2 (t)) respectively measured by the first and second sensors are minimal.