With the proliferation of mobile devices, mobility management has been one of critical research issues. To make high quality mobility management protocol, PMIPv6 is developed. However, to use PMIPv6 widely in the real world, security issues must also be considered. Authentication is the most basic solution to protect many security threats, but detailed authentication procedure is not specified in the PMIPv6 standard document. So, many researchers have proposed their own authentication schemes. Most of these schemes assume that there is only one PMIPv6 domain. Recently, inter-PMIPv6-domain handover schemes, which consider multiple domain environments, were devised to enable PMIPv6 to cover much larger area, but little research has been done about authentication procedure of inter-domain handover. In this paper, we propose a public key based PMIPv6 authentication scheme. According to our analysis, proposed scheme shows better performance than other previous works.