The invention comprises the steps of storing immersed or smothered raw
material of soy beans including hulls in a storage chamber provided at
the front part of a cylinder barrel, subsequently passing the stored raw
material of soybeans through screens furnished at the front end of the
cylinder barrel by driving a piston, and urging to press it out, thereby
to manufacture a milk of the soy beans of the raw material being
extremely refined. At this time, the screens are 60 to 500 meshes, and
the pressure is 8.0 to 55.0 MPa.