Recently, with the development of wireless communications and mobile computing, interest in mobile computing is rising. Mobile computing can be regarded as an environment where a user carries mobile devices and shares resources with a server via wireless communications. A mobile database, which can be used in the various fields, refers to a database used in these mobile devices. Especially, LBS which utilizes location information of users becomes an essential field of mobile computing. In order to support LBS in the mobile environment, there must be an Embedded Spatial MMDBMS that can efficiently manage large spatial data in spatial mobile devices. Therefore, in this paper, we developed an Embedded Spatial MMDBMS, extended from the HSQLDB which is an existing MMDBMS for PC, to manage spatial data efficiently in spatial mobile devices. The Embedded Spatial MMDBMS adopted the spatial data model proposed by ISO, provided the arithmetic coding method suitable for spatial data, and supported the efficient spatial index suitable for spatial mobile devices. In addition, the system offered the spatial data display capability and supported the data caching and synchronization capability between the Embedded Spatial MMDBMS and the GIS server.