Sony Ericsson’s new Walkman line of music phones carried the joint venture into one of its most profitable quarters. The Japanese-Swedish vendor posted Q1 profits of Euro 109 million ($132 million), more than triple the Euro 33 million it posted the same quarter a year earlier.

Sony Ericsson shipped 13.3 million handsets in first three months of 2006, up from 9.4 million in the same period in 2005. Though shipments were down from the 16.1 million units shipped in the fourth quarter of 2005, Q4 shipments are usually the highest volume months for phone vendors due to the holidays, and Sony Ericsson officials said they are still beating industry averages for growth. While the phone-maker said that growth was spurred by sales in developing and developed markets, its Walkman line had a huge impact. Though the company didn’t break out Walkman phone shipments, its average handset sales price rose 9.3% to 149.8 Euros ($181.45), indicating that the pricier Walkman and Cyber-shot high-end camera phones are pulling more weight.

That increased selling price led to 56% increase in revenues year-over-year, from Euro 1.29 billion in Q1 of 2005 to Euro 1.99 billion last quarter. Sony Ericsson sold 3 million Walkman phones in 2005 though it launched its first device only in August. That was the high-end W800i, but since then the vendor has been scaling down the market, announcing a mass-market music phone earlier this year. Sony Ericsson’s Walkman line has also begun to gain traction with carriers. Cingular has begun carrying its W600i mid-range music-camera phone, and last month Orange announced it would base its mobile music strategy on the Walkman line.