A muller for finely mulling a material to be processed is disclosed. The muller comprises a nozzle unit (10) including feed lines (12a and 12b) and hollow pipe lines (120a and 120b), a mulling unit (20) including a mulling head (22), and an input device (30) including a hopper (310) and a feeder (322). The muller finely mulls the material even if it has a relatively large particle size, and continuously feeds the material while mulling it in order to improve productivity. The muller conducts cold mulling of the material or maintains the temperature thereof by employing a cooling system to prevent the generation of heat due to inter-material collision as the material is transferred, or friction against the feed lines, thereby extending the lifespan of the muller. The muller requires no separate classifier by employing successively arranged mulling units (20a to 20n) to accomplish a high economical efficiency.