Satoru Umeta, 24, was convicted of assaulting singers Rina Kawaei and Anna Iriyama, both 19, along with one of the group's male employees at a "hand-shaking event" for fans in Takizawa City, Iwate Prefecture last May, CNN's affiliate TV Asahi reported.
The attack left the three victims severely injured, according to Japan's Kyodo news agency.
Handing down the sentence in the Morioka District Court, Judge Takehiko Okada said that the consequences of the attack -- which involved a foldable saw fitted with box cutter blades -- could have been worse.
"What he did was a dangerous act that might have claimed the lives of the victims," said Okada.
The unemployed Umeta had been motivated to commit the attack out of his frustration at failing to find a job, the judge said.
The month after the attack, Kawaei appeared amid tight security at a stadium in Tokyo for the group's "general election" to hear the results of a ballot as to who would lead the band for the coming year.
Named for Tokyo's Akihabara district, where the group has a theater, and the number of members in its initial lineup, the band holds the Guinness Record for being the world's largest pop group.
Engineered to be accessible to its passionate fanbase, the group is subdivided into various units, allowing one team to perform while the others tour, promote or record.
Concerts at their theater are so popular that tickets for the daily performances are allocated on a lottery system.
The formula has made AKB48 one of Japan's best-selling musical acts, and won them fans elsewhere in Asia, with "sister groups" in Indonesia, Taiwan and China.
But the group has also attracted its share of criticism, with questions raised over its occasionally sexualized lyrics, and the group's management accused of exploiting its young charges.
In February 2013, eyebrows were raised when member Minami Minegishi appeared in a YouTube video
with a shaven head, making a tearful apology for having stayed the night at a male friend's place -- against the group's strict code of conduct.