The author proposes a method to build a relational database of software requirements specifications (SRSs) from textual and visual SRSs automatically. The author has been developing a requirements model named Requirements Frame, a text-base requirements language and a visual requirements language based on the model in order to improve the quality of SRSs. Since Requirements Frame can be transformed into relational data model, each of requirement sentences can be regarded as a tuple of a relational table. The author has been developing both a query language and a relational database management system for an SRS database. One of the features of the SRS DB system is to show an answer with a requirement sentence as an example/counter-example. This feature contributes to verify the SRS from a developer's own viewpoint. Another feature is to detect changed requirements in modification of the SRS. This feature contributes to effective maintenance of the SRS.