A method of manufacturing a solid granule for use as or in a cleaning agent includes providing an anionic surfactant component having at least one anionic sulfonate surfactant and at least one anionic fatty alcohol-based sulfate surfactant; providing a granule-forming agent; mixing the anionic surfactant component and the granule-forming agent into a solid mixture; receiving the solid mixture in a granulation device, the granulation device having a first roller cutter and a second roller cutter, the first roller cutter includes a plurality of first blades and a plurality of first grooves, the second roller cutter having a plurality of second blades and a plurality of second grooves; cutting the solid mixture into a rough granule by cooperating the first blades with the second blades; and polishing the rough granule into the solid granule by friction rubbing between the first grooves and the second grooves.