It is known that the environment condition (e.g. temperature, air velocity, etc.) give influence to outgassing characteristic of the gaseous organic compound emitted from building material. However, there is not little of report that humidity gives influence to outgassing characteristic. We show that the gaseous organic compound emitted from building material receives influence of moisture contained into building material. At first, we conducted the experiment about adsorption behaviour of moisture. Next, we grasned the change of gas emission flux when humidity was changed. Results are as follows ; 1) When humidity became high, a quantity of moisture contained into building material increased. In particular the surface adsorption moisture increased in exponential. 2) When it was high humidity condition, a quantity of emission of gaseous organic compound increased. 3) It is considered that the surface adsorption moisture influenced outgassing behaviour after humidity had changed.