The decision paved the way for former Aum Shinrikyo cult guru Shoko Asahara to be executed, Kyodo News agency and public broadcaster NHK said. Defence lawyers were not immediately available for comment.
The Tokyo High Court had rejected the defenceís appeal against the death sentence in March, prompting Asaharaís lawyers to file an objection.
Todayís decision overruled the objection, although NHK reported that another appeal is possible.
Asaharaís lawyers objected to the original ruling, saying it was based on a mistaken psychiatric assessment.
Asahara, born Chizuo Matsumoto, was convicted in 2004 and sentenced to hang for masterminding the 1995 Tokyo assault, in which members of the doomsday group released deadly sarin gas on city trains.