The present invention relates to a coacervate comprising a mussel adhesive protein and an anionic polymer, and more particularly, to a coacervate prepared by mixing a mussel adhesive protein with an anionic polymer, and a novel use thereof. In the present invention, a coacervate prepared by mixing a mussel adhesive protein and an anionic polymer shows a very excellent adhesive strength to various substrates such as cells or metals, and is able to maintain its adhesive strength in the presence of water or under water, thereby being effectively used as an adhesive. Moreover, it has an activity capable of encapsulating bioactive materials, thereby being effectively used as an active component of a composition for delivering bioactive materials.
