A tube consisted of chitin/chitosan nanofibers is one of the candidates to support nerve regeneration. However, chitin/chitosan would cause inflammation when implanted in human body. This study indicates that chitosan nanofibers (degree of deacetylation; 78% and 93%) could be modified by alternate soaking in calcium and phosphate solutions, resulting in the improvement of their biocompatibility in terms of both in vitro cell culture experiment and in vivo animal test. Deacetylation of the chitosan nanofibers appeared to have little effect on ill vitro and in vivo behaviors after 3 days. However, the alternate soaking process clearly improved in vitro and ill vivo responses against the chitosan nanofibers. During the process, the surface morphology of the chitosan nanofiber was not changed, i.e. no hydroxyapatite was deposited due to the limited number of soaking. Thus, the surface chemical and physical states of the modified chitosan nanofiber such as surface charge, surface free-energy, and wettability was found to influence both the cell attachment and inflammation. [doi:10.2320/matertrans.ME200826]