For autonomous service robots used in our daily environment, such as a personal mobility vehicles or delivery robots, localization is one of the most important and fundamental functions. A number of localization techniques, including simultaneous localization and mapping, have been proposed. Although a Global Navigation Satellite System (GNSS) is most commonly used in outdoor environments, its accuracy is around 10 meters and so is inadequate for navigation of an autonomous service robot. Therefore, a GNSS is usually used together with other localization techniques, such as map matching or camera-based localization. In the present study, we adopt the Quasi-Zenith Satellite System (QZSS), which became available in and around Japan on November 2018, for the localization of an autonomous service robot. The QZSS provides high-accuracy position information using electronic reference points and four quasi-zenith satellites, and has a localization error of less than 10 centimeters. In the present paper, we compare the positioning performance of the QZSS and real-time kinematic GPS, and verify the stability and the accuracy of the QZSS in an outdoor environment. In addition, we introduce a tour guide robot system using the QZSS and present the results of a guided tour experiment in a theme park.