- 2023/06 - 現在 President, Japan Society for Industrial and Applied Mathematics (JSIAM)
- 2021/04 - 現在 The Graduate University for Advanced Studies Professor Emeritus
- 2021/04 - 現在 Professor Emeritus, National Institute of Informatics
- 2018/06 - 現在 Fellow, Japan Society for Industrial and Applied Mathematics (JSIAM)
- 2006/04 - 2021/03 Professor, Principles of Informatics Research Division, National Institute of Informatics
- 2004/04 - 2021/03 Professor, Department of Informatics, School of Multidisciplinary Sciences, The Graduate University for Advanced Studies
- 2006/04 - 2008/03 Head, Department of Informatics, School of Multidisciplinary Sciences, The Graduate University for Advanced Studies
- 2001/01 - 2006/03 Professor, Mathematical Informatics, Foundations of Informatics Research Division, National Institute of Informatics
- 2002/04 - 2004/03 Professor, Department of Informatics, School of Mathematical and Physical Science, The Graduate University for Advanced Studies
- 1995/04 - 2000/12 Associate Professor, Department of Mathematical Engineering and Information Physics, Graduate School of Engineering, The University of Tokyo
- 1993/04 - 2000/12 Associate Professor, Department of Mathematical Engineering and Information Physics, Faculty of Engineering, The University of Tokyo
- 1997/04 - 1998/01 Visiting Associate Professor, Department of Mathematics, Kiel University, Germany
- 1991 - 1993/03 Research Manager, C&C Information Technology Research Laboratories, NEC Corporation
- 1981/04 - 1993/03 Research Laboratories, NEC Corporation
- 1986/09 - 1988/05 Visiting Researcher, Wessex Institute of Technology, U.K.