Controlling indoor relative humidity is of great importance in the evaluation of thermal comfort and perceived air quality. This study aimed to develop a new mineral fiber board as an interior surface material with high capacity of moisture adsorption and desorption. A series of experiments were carried out in this study using an accurately controlled chamber, mock-up rooms, and real-scale test houses. The chamber test was conducted to measure the moisture adsorption and desorption content of the materials. In the mock-up rooms, the effects of the new mineral fiber board on indoor humidity were investigated under three different conditions. The three different conditions include: 1) a mock-up room with an electric humidifier, 2) a mock-up room with an open water basin, and 3) a mock-up room without artificial humidifying measures. In the real-scale test houses, the efficiency of the new mineral fiber board was also investigated under two different conditions of low-humidity and very high-humidity. Through the chamber test, it was found that the moisture adsorption content of the new mineral fiber board was three times more than that of the ordinary mineral fiber board. The moisture desorption content of the new board was also two and half times more than that of the ordinary mineral fiber board. In the mock-up test, the newly developed mineral fiber board could also control indoor humidity levels effectively by desorbing moisture under low humidity conditions. However, through the real-scale test, it was found that the new mineral fiber board could not absorb or desorb indoor moisture effectively if extremely dry or humid conditions last for a long time. Overall, the new mineral fiber board was proven to be effective in controlling indoor moisture except under extremely dry or humid conditions.