In recent years, global warming has become a world problem. So reduction of carbon dioxide is required in all industries against global warming. Focusing on the construction, Portland cement which is the most widely used construction material discharges large amounts of carbon dioxide during the manufacturing process. Therefore, the use of mixed cement replacing admixture materials such as ground granulated blast furnace slag and fly ash with Portland cement is receiving a lot of attention. Mixed cement has advantages such as effect of protected penetrated chloride ion, prevent of ASR, enhancement of long-term strength, etc. However, it has been reported that drying shrinkage of cement with high content of ground granulated blast furnace slag becomes large. Cracks of drying shrinkage cause decreasing resistance of the durability on concrete structures. Therefore, countermeasures to reduce drying shrinkage are essential. So we focused on fly ash in this research. In the past researches, it has been reported to reduce drying shrinkage using fly ash. So it is expected that reduction of drying shrinkage can be expected, even in cement with high replacement ground granulated blast furnace slag. Therefore, in this study, mortar with fly ash added to blast furnace slag cement was made for the purpose of reducing drying shrinkage in blast furnace slag cement, and drying shrinkage were measured. In addition, since the drying shrinkage is closely related to the pore diameter and the pore volume of the mortar, the measurement of the pores was carried out from a mercury intrusion porosimetry. And the drying shrinkage is reduced in the mortar having the high replacement rate of the ground granulated blast furnace slag. We also confirmed the effect of reducing the drying shrinkage of FA.