PURPOSE: To eliminate breakage of a fiber by premixing the fiber with a fixed component, giving a vibration energy to a mixture moistened with fluid, placing the mixture moistened with the fluid under pressure while applying the energy to mix the fiber with the component, and facilitating a reaction of the fluid with cement.

CONSTITUTION: When a form filled with a wet body is placed on a table after a premixture is moistened, the form is clamped with it, operated with a press, a cover plate 102 is brought into contact with an upper surface of a wet material, and further a required pressure is applied to the mixture. A vibration mixing unit 82 is calibrated so that a frequency range optimum for various sheet references is decided. Then, the material is closely mixed by a slight motion of particles, and a vibration mixture is facilitated by a frequency of a specific range for a specific state at a point of admixing a cement paste with sand and the fiber without altering a random distribution of the fiber. The cement particles are pulverized by the vibration, water is brought into contact with the cement of a further large range to facilitate its hydration.