Authorities said 63-year-old Sumitoshi Tsuda, convicted of killing three people in 2009, was hung Friday in Tokyo.
Japan launched a jury system in 2009 that calls for citizens to deliberate with professional judges in a bid to boost the role of the citizenry in the courtroom. Tsuda was the first man convicted by lay judges to be executed.
"Lay judges made the very grave judgment, and I took it seriously," Justice Minister Mitsuhide Iwaki told reporters.
The Mainichi newspaper reported that Tsuda was found guilty for killing a neighbor and two others with a knife after he said they were making too much noise opening and shutting his door. He withdrew his appeal after the conviction.
Also hung on Friday was 39-year-old Kazuyuki Wakabayashi, convicted of killing a woman and her daughter in 2006. He had initially pleaded guilty but later claimed his innocence. He was hung in the city of Sendai.
International outcry overruled
The latest executions prompted angry reaction from international campaigners, who called on Japan - the only industrialized country other than the United States with capital punishment - to abolish the death penalty.
"The death penalty is not justice or an answer to tackling crime, it is a cruel form of punishment that flies in the face of respect for life," Roseann Rife, an East Asia researcher with Amnesty International said. "Japan should immediately introduce an official moratorium on executions as a first step towards abolition of the death penalty."
Surveys, however, have shown the death penalty - carried out 14 times since 2012 - is popular in Japan, despite repeated protests from European governments and human rights groups.
Japan now has 127 inmates on death row whose conditions are needlessly harsh, according to anti-death penalty campaigners.
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