OBJECTIVES: Considering official introduction of pharmacoeconomic requirements in Japanese healthcare policy in 2016, we aimed to assess whether the quality of pharmacoeconomic studies in Japan has been improved over time, and what aspects are in need for further improvement. METHODS: The literature review approach was taken for English-language articles via PubMed (Japan AND "Cost-Benefit Analysis"[Mesh]) and Embase (Japan AND cost effectiveness), and also for Japanese-language via Web service of Japan Medical Abstracts Society (“hiyo-tai-koka” in Japanese, which means “cost-effectiveness”), excluding review articles, commentaries, methodological studies, and letters. After eligibility screening, we eventually obtained 174 articles as subjects, which were summarized and assessed regarding the quality of reporting on whether to state the five factors explicitly: 1) study perspective, 2) reason of discount rate, 3) year of currency, 4) time horizon, and 5) comparator. For each of those factors, we examined a proportion of satisfaction, i.e., a percentage of the articles having clearly described the target factor among all the articles. In addition, the proportions were compared by the other nominal factors such as founding source, intervention type, and QALY employment. RESULTS: The number of publications has been increasing over time. Over 60 % of studies, however, did not clearly disclose their funding sources. The studies without any funding disclosure revealed less satisfaction in each of the five factors. Those with disclosure of industry-funding had higher satisfaction rates compared to the studies with public-funding disclosure or without funding disclosure. Although the studies which employed QALY as the outcome measure earned high satisfaction of the five factors, no totally positive improvement was observed over time in terms of satisfaction for any of the five factors. CONCLUSIONS: The quality of reporting the Japanese health economic evaluations was not yet satisfactory, and remains further challenges for quality improvement to comply with the international standards.