The invention discloses an infrared dried soft sludge body granulator which comprises a support and a drying cylinder supported on the support. A sludge hopper for adding sludge into the drying cylinder is arranged on the drying cylinder, a roller mechanism for rolling fed sludge is arranged in the drying cylinder and located below the sludge hopper, a flat belt conveying mechanism is arranged below the roller mechanism, multiple trays arranged in the height direction of the drying cylinder at intervals and driven by a shaking mechanism are arranged below the flat belt conveying mechanism, multiple holes are formed in the tray, the multiple trays include first trays and second trays, the first trays and the second trays are arranged in a staggered mode, a heating mechanism for heating the sludge is also arranged in the drying cylinder, an air outlet pipe is arranged at the top of the drying cylinder, and a sludge granule outlet is formed in the bottom of the drying cylinder. In addition, the invention further provides a granulation method. The granulator and the granulation method make granulation uniform, and the cost is low.