A masterbatch manufacturing method in accordance with the present disclosure comprises an operation in which pre-coagulation rubber latex comprising filler is coagulated to obtain a coagulum; an operation in which the coagulum is dewatered; and an operation in which the dewatered coagulum is plasticized as it is dried by means of an extruder; wherein, during the operation in which the dewatered coagulum is plasticized as it is dried, the coagulum comprises a peptizing agent.