Softbank Corp. almost doubled its group net profit in fiscal 2010 from to a record ¥189.71 billion on robust operations in its mainstay mobile phone service division.

Its consolidated operating profit for the year that ended March 31 rose 35.1 percent to ¥629.16 billion as sales expanded 8.7 percent to an all-time high of ¥3.00 trillion, the firm said Monday.

The mobile phone service division boosted sales 14.3 percent to ¥1.94 trillion by expanding the number of its mobile phone customers by 3.53 million to 25.4 million and mobile phone sales by 1.11 million units to 10.24 million units on the strength of the popular Apple iPhone handset.

The Softbank group increased its share of the domestic mobile phone service market by 1.8 percentage point to 21.3 percent, the company said.

Smartphones will overtake regular mobile phones in Japan in the year ending March 2013, reaching 19.3 million units, Tokyo-based MM Research predicted in December. Shipments of the devices will climb to 24.1 million in fiscal 2015, the research firm said.

The iPhone was Japan's most popular smartphone in the six months that ended in September, capturing 60 percent of the shipments in the country, according to MM Research.

Sony Ericsson Mobile Communications AB's Xperia was second with 21 percent, followed by Sharp Corp.'s model with 6.3 percent. Both of those phones run on the Android operating system.