The purpose of the invention of the present application is to provide a method for preparing a hydrogel composed substantially only of nucleic acids. The invention of the present application provides: a nucleic acid sol-like composition for producing a nucleic acid gel without requiring the use of any nucleic acid ligase, wherein the composition comprises at least two nucleic acid monomers which are partly complementary to each other and are independently selected from the group consisting of a nucleic acid, a nucleic acid derivative, a modified nucleic acid, a compound capable of binding to a nucleic acid in a complementary manner and a mixture thereof, one of the nucleic acid monomers has a moiety that constitutes a cohesive protruding end and a complementary nucleotide sequence moiety that can bind t at least one of the other nucleic acid monomers to form a double strand, and the composition contains no nucleic acid ligase and a nucleic acid gel produced using the composition.
