For the development of a food-grade expression system for Bifidobacterium, a strong promoter leading to high-level expression of cloned gene is a prerequisite. For this purpose, a promoter screening host-vector system for Bifidobacterium has been established using ${eta}$-glucosidase from Bifidobacterium lactis as a reporter and Bifidobacterium bifidum BGN4 as a host, which is ${eta}$-glucosidase negative strain. Seven putative promoters showing constitutive high-level expression were selected through microarray analysis based on the genome sequence of B. bifidum BGN4. They were cloned into upstream of ${eta}$-glucosidase gene and transformed into Escherichia coli $DH5{alpha}$ and B. bifidum BGN4. Promoter activities were analyzed both in E. coli and B. bifidum BGN4 by measuring ${eta}$-glucosidase activity. ${eta}$-Glucosidase activities in all of the transformants showed growth-associated characteristics. Among them, P919 was the strongest in B. bifidum BGN4 and showed maximum activity at 18 h, while P895 was the strongest in E. coli $DH5{alpha}$ at 7 h. This study shows that novel strong promoters such as P919 can be used for high-level expression of foreign genes in Bifidobacterium and will be useful for the construction of an efficient food-grade expression system.