The present invention addresses the problem of providing a method for manufacturing a preparation which contains acetaminophen at a high content, in particular, a size-reduced tablet (common tablet, sustained-release tablet, etc.) which has excellent elution properties, preferable hardness and high drug content uniformity, and a premix drug substance of acetaminophen which has improved manufacturability. According to the method of the present invention wherein acetaminophen having a preset particle size is used for manufacturing a preparation, the flowability of acetaminophen can be improved so that secondary aggregation can be suppressed and manufacturing efficiency can be elevated. Thus, this method is highly useful for manufacturing an acetaminophen preparation having improved administrability, for example, a reduced size.
