Pure zeolite beta was synthesized by conversion of magadiite in solid state with the assistance of seeds for the first time, and the influence of synthesis parameters was discussed in detail. To get further insights into the conversion process, changes of building units and crystallization mechanism were studied by X-ray diffraction, electron microscopy, FT-IR spectroscopy, and solid-state MAS NMR spectroscopy: most parts of 5Rs and 6Rs in magadiite were preserved in the conversion course, and the appearance of 4Rs, which could be a key to the growth of zeolite beta, was promoted by rearrangement and connection of preserved 5Rs. A trace of constitution water existing in the layer structure of magadiite would be important for a successful conversion because it could facilitate the condensation of aluminosilicate species into the beta framework.