The MAGIC Collaboration is building a second telescope, MAGIC II, improving the design of the current MAGIC Telescope. MAGIC II is being built at 85 m of distance from MAGIC I, and will also feature a huge reflecting surface of ∼ 240 m of area. One of the improvement is the design for the mirror of MAGIC II, that are lighter and larger, being square of 1 m of side and weighting around 15 kg. For the development and production of the new mirrors, two different techniques, both reliable and affordable in price, were selected: the diamond milling of aluminium surfaces and the cold slumping of thin glass panes. As tests for the second one are still ongoing, we present a description of the diamond milling technique, and its application and performance to the produced mirrors.