Seven biosimilar products have been approved in Japan since the March 2009 publication of the ‘Guideline for quality, safety and efficacy assurance of biosimilar products’ by the Ministry of Health, Labor and Welfare (MHLW). Four years previously, the ‘Guideline on similar biological medicinal products’ was issued in the European Union (EU), and 13 products as of February 2016 have been approved as biosimilar. The US Food and Drug Administration (FDA) approved the first biosimilar product in the US in March 2015 and final Guidance was issued at the end of April 2015. Over the past decade, the challenges regarding the development of biosimilar products have been discussed extensively. In this article, the data packages of biosimilar products in Japan are compared with those overseas in order to clarify the concepts used by the Japanese regulatory authority, i.e., the Pharmaceuticals and Medical Devices Agency (PMDA). The challenges in the development of biosimilar products in Japan are also addressed.