The object of the present invention is to provide a novel fluorescent protein in which on and off of fluorescence thereof can be controlled by irradiation with lights of two different wavelengths. The present invention provides a fluorescent protein shown in the following (a) or (b); (a) a protein which has the amino acid sequence shown in SEQ ID NO: 3 or 7; or (b) a protein which has an amino acid sequence comprising a deletion, substitution, and/or addition of one or several amino acids with respect to the amino acid sequence shown in SEQ ID NO: 3 or 7, and which has fluorescence characteristics of exhibiting a photochromic effect.