The Yokohama District Court sentenced the operator of a small private nursery in Yamato, Kanagawa Prefecture, to 20 years in prison Monday for killing two babies through physical abuse and seriously injuring four others.
Junko Izumo, 31, who ran the nursery Smile Mum Yamato Room, pleaded guilty to injuring a baby boy but denied all of the other charges.
The nursery no longer operates.
A 20-year prison term is the maximum fixed prison sentence in Japan.
Presiding Judge Hiroshi Yamura, in handing down the sentence sought by prosecutors, said her actions constituted "an extremely brutal crime against infants and small children who could not fight back or alert anyone to the abuse. There is no room for leniency."
The judge added that Izumo continued the violence for about a year.
Izumo nodded her head when the judge delivered the sentence.
Izumo was found guilty of physically abusing a 1-year-old boy and causing his death on Feb. 4, 2000, and of causing the death through physical abuse of a 2-year-old boy 14 days later.
She was also found guilty of physically abusing four infants, aged 8 months to 2 years old, on five occasions, one of them twice, between June and September 1999, leaving them with serious injuries.
Lawyers for Izumo said the ruling was "very regrettable" and they will consult with their client to decide whether to appeal.
The mother of the dead 2-year-old boy testified during the trial: "I have the urge from the court gallery to hit her. I blamed myself for putting my son in the defendant's hands, and have contemplated suicide."