The purpose of the present invention is to provide a simple method for measuring autophagy that makes it possible to measure autophagy activity accurately and quantitatively. Provided are a fusion protein fusing an LC3 protein including a first tag and a protein including a second tag, nucleic acid including a base sequence encoding this fusion protein, a vector including this nucleic acid, cells or transgenic nonhuman organisms having at least this nucleic acid and/or this vector introduced, and a method for measuring autophagy using these cells or transgenic nonhuman organisms.