This paper presents about the localization technology to estimate the positions of the mobile robot that is able to navigate through the multi-floor spaces, for expanding the application ranges of the robots. For this purpose, the mobile robots can use some maps having some information about the spaces in advance. In this paper, the maps are divided into two types according to the application; as to one, it is the grid-based map that represents the locations and the structures of objects in the robot surroundings with each floor. The other is the inter-floor map containing the stairs data to help the robot move into other floors. And the localization method is consisted of the floor and the inter-floor localizations. The floor localization uses the particle filter method to estimate the robot position in each floor. And the inter-floor localization can help the robot safely move to other floors by recognizing the stairs and change the coordinate system. Finally we performed the experiments in the multi-floor office spaces to verify the effectiveness of the proposed localization method by using the robot with the caterpillar wheels and the maps.