A device for manufacturing a suspension by mixing together a plurality of materials, the device comprising: a container that accommodates the materials; first blades rotatably arranged in the container; and a second blade rotatably arranged to surround the first blades, the second blade including vertical blade portions that each have a predetermined width in a radial direction of the container, and that extend in an up-down direction, and each creating a predetermined clearance with an inner side surface of the container, and horizontal blade portions respectively having end portions coupled to lower end portions of the vertical blade portions, and other end portions extending inwardly in the radial direction, the second blade having the predetermined clearance between each of the vertical blade portions and an inner side surface of the container, wherein the device further comprises first rotation means that causes the first blades to rotate; second rotation means that causes the second blade to rotate; and rotation drive control means that controls the first rotation means and the second rotation means, the rotation drive control means causing the first blades to rotate faster than the second blade, wherein the rotation drive control means is configured to rotate the first blades and the second blade in directions opposite to each other to cause the first blades to generate a downward flow in the container for mixing together the materials, and, rotate the first blades and the second blade in an identical direction to cause the first blades to generate an upward flow in the container for degassing the materials, wherein the rotation drive control means is configured to rotate the first blades at a speed falling within a range from 600 to 1800 rpm, and rotate the second blade at a speed falling within a range from 3 to 20 rpm. a container that accommodates the materials; first blades rotatably arranged in the container; and a second blade rotatably arranged to surround the first blades, the second blade including vertical blade portions that each have a predetermined width in a radial direction of the container, and that extend in an up-down direction, and each creating a predetermined clearance with an inner side surface of the container, and horizontal blade portions respectively having end portions coupled to lower end portions of the vertical blade portions, and other end portions extending inwardly in the radial direction, vertical blade portions that each have a predetermined width in a radial direction of the container, and that extend in an up-down direction, and each creating a predetermined clearance with an inner side surface of the container, and horizontal blade portions respectively having end portions coupled to lower end portions of the vertical blade portions, and other end portions extending inwardly in the radial direction, the second blade having the predetermined clearance between each of the vertical blade portions and an inner side surface of the container, wherein the device further comprises first rotation means that causes the first blades to rotate; second rotation means that causes the second blade to rotate; and rotation drive control means that controls the first rotation means and the second rotation means, the rotation drive control means causing the first blades to rotate faster than the second blade, wherein the rotation drive control means is configured to rotate the first blades and the second blade in directions opposite to each other to cause the first blades to generate a downward flow in the container for mixing together the materials, and, rotate the first blades and the second blade in an identical direction to cause the first blades to generate an upward flow in the container for degassing the materials, wherein rotate the first blades and the second blade in directions opposite to each other to cause the first blades to generate a downward flow in the container for mixing together the materials, and, rotate the first blades and the second blade in an identical direction to cause the first blades to generate an upward flow in the container for degassing the materials, the rotation drive control means is configured to rotate the first blades at a speed falling within a range from 600 to 1800 rpm, and rotate the second blade at a speed falling within a range from 3 to 20 rpm. rotate the first blades at a speed falling within a range from 600 to 1800 rpm, and rotate the second blade at a speed falling within a range from 3 to 20 rpm.