| 1954 | Formation of a working group for the foundation of an institute for nuclear study. | |
| 1955 | The Institute of Nuclear Study (INS) was established. | |
| 1957 | Sep:FF cyclotron was completed. | |
| 1958 | May:FM cyclotron was completed. Jun:The first experiment with the FF cyclotron took place. | |
| 1960 | Oct:The first experiment with the FM cyclotron took place. | |
| 1961 | Dec:The Electron Synchrotron (ES) accelerated an electron beam to 750 MeV. | |
| 1963 | Apr:The first experiment with the ES took place. | |
| 1964 | Apr:Formation of a working group for the foundation of a new research institute for elementary particle physics. | |
| 1966 | Mar:The ES produced a 1.3 GeV beam. | |
| 1971 | Apr:National Laboratory for High Energy Physics (KEK) was established. | |
| 1976 | Mar:The proton synchrotron (PS) produced an 8 GeV beam as designed. Dec:The PS achieved 12 GeV. | |
| 1977 | May:The first PS experiment took place. | Dec:Experiments with the SF cyclotron began. |
| 1978 | The Booster Synchrotron Utilization Facility and a Photon Factory (PF) were founded. | The Meson Science Facility was established. |
| 1980 | Jul:Experiments in the Booster Synchrotron Utilization Facility began. | |
| 1982 | Mar:The PF succeeded in storing a 2.5 GeV electron beam. | |
| 1983 | Jun:PF Experiments began. | |
| 1984 | Jul:The TRISTAN Accumulation Ring (AR) accelerated an electron beam to 6.5 GeV. | |
| 1985 | Oct:The AR accelerated a positron beam to 5 GeV. | |
| 1986 | Nov:The TRISTAN Main Ring (MR) accelerated both electron and positron beams to 25.5 GeV. | |
| 1987 | May:TRISTAN experiments began. | |
| 1988 | Apr:The Meson Science Facility was reorganized as a Laboratory (MSL) Nov:The MR energy was upgraded to 30 GeV with the help of superconducting accelerating cavities. | |
| 1989 | Accelerator and Synchrotron Radiation Science departments were established in the Graduate University for Advanced Studies | Sep:First electron cooling by TARNII |
| 1993 | Mar:Isotope Separator On-Line (ISOL) was completed. | |
| 1994 | Jun:KEKB B-factory construction began. | |
| 1995 | Dec:TRISTAN experiments finished. | |
| 1997 | The High Energy Accelerator Research Organization was established. | |
| 1998 | First beam storage at KEKB (KEK B-factory) ring | |
| 1999 | Apr:The Department of Particle and Nuclear Science was founded in the Graduate University for Advanced Studies. May:The Long-baseline Neutrino Oscillation experiment (K2K) began. Jun:The Belle experiment at the KEK B-factory began operation. | |
| 2000 | Tanashi Branch closed | |
| 2001 | Construction of High Intensity Proton Accelerators (J-PARC) started | |
| 2004 | Apr:Became the Inter-University Research Institute Corporation High Energy Accelerator Research Organization. Nov:K2K experiment ended | |
| 2005 | Apr:Tokai Campus was opened. Dec:Experiments at PS ended. | |
| 2006 | Feb:J-PARC Center was established. Mar:Experiments at BSF ended. | |
| 2007 | Jan:181MeV proton beam at J-PARC Linac Oct:3 Gev proton beam at J-PARC Rapid Cycling Synchrotron (RCS) | |
| 2008 | Oct:Prof. Makoto Kobayashi, former director of IPNS, won the 2008 Nobel Prize in Physics. | |
| 2009 | Mar:J-PARC construction was completed. | |
| 2010 | Jun:The Belle experiment ended | |
| 2011 | Construction of the SuperKEKB started | |
| 2016 | Phase 1 operation of the SuperKEKB started |