To provide a method for improving the blocking rate of a permeable membrane, which can reduce lowering in permeation flux of the permeable membrane to improve the blocking rate, particularly against organic matter, and thus to realize a high organic matter removing effect and stable treatment, and to provide a permeable membrane, a permeable membrane treatment method, and a permeable membrane apparatus.

A blocking rate improving agent 15 of a hydrophilic polymer is supplied to a primary side 3 of a permeable membrane module 1 to deposit the blocking rate improving agent onto the permeable membrane 2 and thus to improve the blocking rate of the permeable membrane 2. Thereafter, a modification agent 16 of a water soluble polymer containing a hydrophobic group is supplied to deposit it on the permeable membrane subjected to the blocking rate improving agent treatment, to modify it to further improve the blocking rate.