Microtubes of alpha-K4SiW12O40 with the length around 1 cm and inner diameter and wall thickness in the ranges of 7 - 55 mu m and 3 - 15 Am, respectively, were copiously fabricated by a one-step, template-free aqueous synthesis. The formation mechanism is discussed. The discovered tubular structure of the polyoxometalate is believed to be promising for use in templates, as a precursor of tungsten oxide ceramic microtubes, and for other uses associated with tubular structures.