PROBLEM TO BE SOLVED: To provide a block for marine algae proliferation in which marine algae grow easily. SOLUTION: The block for marine algae proliferation includes a pedestal block 10 that has two or more legs 111, 112, 113, one or more attachment/detachment parts 201, 202 arranged on the pedestal block, and one or more upper blocks 301, 302 installed on the attachment/detachment parts 201, 202, wherein one or more of the pedestal block 10 and the upper blocks 301, 302 contain iron slag and an essential amino acid. COPYRIGHT: (C)2012,JPO&INPIT