In Japan, postal services are privatized since October 2007, and the Japanese Government plans to sell off the stocks of postal financial enterprises (Japan Post Insurance Co. Ltd. and Japan Post Bank Co. Ltd.) in coming years. Looking for an appropriate privatization process of postal services, this paper intends to analyze the experience of New Zealand, which is said to be a global leader in terms of the privatization of postal services. In particular, we focus on Kiwibank, which was established as a state owned enterprise (SOE). The primary aim of this paper is to throw the light on the competitive impact of the establishment of Kiwibank on the foreign mega-banks, which had enjoyed monopolistic rents after New Zealand's liberalization of capital investment and the sale of New Zealand Post Bank to a foreign mega-bank.