An objective of the present invention is to provide promoters having seed-specific promoter activity, and methods of expressing foreign proteins in seeds. The present inventors isolated the promoter of ADP-Glucose pyrophosphorylase which is expressed in rice seeds, constructed binary vectors in which the ADP-Glucose pyrophosphorylase promoter is inserted upstream of the GUS reporter gene, and transformed rice using the Agrobacterium method. GUS expression level was used as an index to examine the site of expression, the expression pattern during seed maturation, and the level of expression in seeds for the ADP-Glucose Pyrophosphorylase promoter. Expression was found in the embryo during early stage of maturation and in the entire seed during maturation. Expression in late stage of maturation in embryo was very high.