Nowadays, a computer simulation technique that can analyze radiation transport in material is quite essential for progressing researches in the field of radiation science. In our group, we conduct researches to develop Particle and Heavy Ion Transport code System, PHITS, and to improve its reliability. PHITS is distributed to outside organizations where researchers and technician can apply the code to researches and developments for industrial, scientific and medical fields. We also conducting researches and developments radiation dose assessments for radiological protection, damages in material due to irradiation of radiation, medical physics, calculations of cosmic-rays, geosciences and so on.