The Guinness Book of World Records bestowed the title on Minagawa following the death of Emma Faust Tillman, who was also 114, in the United States.
Staff at the nursing home where Minagawa lives in southern Japan greeted her Tuesday with a poster that said, "Congratulations, you're No. 1."
It took her a while to figure out what all the fuss was about.
"Number one? Who, me?" she said after thinking for a while, according to a nursing home staffer. "My goodness, I'm really grateful," she said, breaking into a big smile.
The nursing home, in the southern Japanese city of Fukuchi, was in a festive mood Tuesday, with Minagawa greeting hordes of well-wishers and reporters. Mayor Koji Urata was among the first, announcing a plan to give her a special award.
Minagawa, who was born Jan. 4, 1893, raised four sons and a daughter on her own by peddling flowers and vegetables after her husband died. Now she has outlived her five children.
The nursing home says she has a healthy appetite, and ventures to the dining room by a motorized wheelchair for meals when she feels up to it.
She has a little trouble hearing, but can communicate fine "if we speak clearly and slowly by her ear," said staffer Mika Tachibana. She chats with friends, combs her hair every morning, and seldom misses the weekly singalong.
"She has a sweet tooth, so we have to watch her, otherwise she reaches out for seconds and thirds," Tachibana said. "She is so youthful, it's hard to believe she is 114.
"Yone-san is our idol and a role model for other residents. We all hope to age like her."
Minagawa has seven grandchildren, 12 great-grandchildren and two great-great-grandchildren, who often visit her, according to the nursing home.
Tillman, the daughter of former slaves, died at a nursing home in Hartford, Conn. Sunday night, just days after assuming the title on Jan. 24 with the death of 115-year-old Emiliano Mercado del Toro of Puerto Rico.
The world's oldest man is also Japanese — Tomoji Tanabe, 111, born Sept. 18, 1895. Tanabe lives in the southern city of Miyazaki, according to Guinness World Records.
Japan has one of the world's longest average life spans.
In 2003, Japanese women set a new record for life expectancy, at 85.3 years, while men live an average of 78.3 years.