In order to improve the deterioration of moisture circumstances have been brought by Japanese weather of which sultry in summer and biting in winter and the prevalence of high airtight and heat insulation without energy, the investigation of autonomous humidity controlling building materials has been done. The capillary condensation phenomenon was utilized for obtaining the autonomous humidity control ability. The relation between the pore size and the relative humidity was expressed by Kelvin's equation. From this equation, it was important that the capillary condensation occurs in the pores around 10nm in diameter from 40 to 70% relative humidity in which human being felt comfortable. The humidity controlling abilities of allophane, the silica gel and gibbsite which had mesopores were investigated and it was clarified that the mixture of gibbsite and clay minerals was appropriate for the interior wall building materials. Therefore the plate sample was prepared from the mixture of gibbsite and clay minerals and studied the humidity control ability. As a result, it showed superior performance.