The Story of Yoshitada and Fumiko Minami, the Inventors of the Automatic Rice Cooker

In post–World War II Japan, cooking rice up to three times a day was an exhausting and labor-intensive task. Housewives often started before dawn, tending traditional fire-powered stoves called kamado—and any slight misstep could result in the harsh judgment of being a “failed housewife.”

During this era, Toshiba assigned a project to Yoshitada Minami—then managing a struggling electric water-heater factory—to create an automatic rice cooker. Though Minami had the technical prowess, he lacked expertise in cooking rice.

Minami turned to his wife, Fumiko—mother of six—to bridge that gap. Over five years, she meticulously documented the perfect rice: measuring water-to-rice ratios, experimenting with temperature profiles, timing, and even testing “in the harshest of conditions”—hot rooftops, cold mornings, and everyday domestic routines.

After years of trial and error, the Minamis, along with Toshiba engineers, discovered a key principle. The perfect rice could be achieved by turning off the heat automatically when the water in the pot had fully evaporated. This rapid increase in temperature (above the boiling point of 100°C) was the signal to stop cooking. Toshiba engineers developed a bimetallic switch that would bend and cut the circuit at this exact moment.

The result was the Toshiba ER-4, the world’s first mass-produced automatic electric rice cooker for home use, launched in 1955. Despite its steep price (about a third of the average monthly salary at the time), it was a massive success. Sales soared—with 200,000 units produced each month within a year. The invention freed women from the daily chore of cooking rice and became a staple in Japanese households, eventually spreading worldwide.

Toshiba’s ER-4, introduced in 1955, was the world’s first automatic rice cooker.

A 1956 advertisement for Toshiba’s world’s first automatic electric rice cooker, priced at 3,200 yen and capable of cooking 900 grams (2.0 lb) of rice.

Their youngest son, Aiji Minami, recalled how the entire family pitched in—helping with testing and even waking up late at night to try new rice cooker prototypes. One breakthrough moment came when Yoshitada presented a working model late at night, leading to a celebrated family tasting: “Ah, this is delicious.”

Fumiko received heartfelt thank-you letters from housewives across the country, which moved her to tears—recognition of a quiet yet profound accomplishment.

The story of Yoshitada and Fumiko Minami is a powerful example of how combining engineering knowledge with real-world user experience can lead to groundbreaking innovation. Fumiko Minami’s often-unrecognized contributions were essential to the success of the automatic rice cooker, making her a true, though unlikely, inventor.