Presiding Judge Takaharu Kondo of the third petty bench made the decision Thursday, upholding the 4-month prison term handed down in district and high court trials against Uekusa for public indecency.
According to the lower courts' rulings, Uekusa, 48, put his hand up the high school student's skirt and touched her body on the night of Sept. 13, 2006, on a commuter train between Shinagawa and Kamata stations on the Keihin Kyuko Line.
Uekusa pleaded not guilty, saying he was mistaken for the real perpetrator.
But the Tokyo District Court convicted Uekusa based on eyewitnesses' testimonies, and the Tokyo High Court affirmed the ruling.
Earlier, Uekusa was convicted of public indecency and fined 500,000 yen for trying to look up a female high school student's skirt using a mirror at a Tokyo railway station in April 2004. He was a professor at Waseda University at that time.