The present invention provides: a method of changing the fluorescence wavelength of a GFP-like fluorescent protein from copepod while maintaining recombinant expression efficiency, which comprises identifying a structural factor for determining the fluorescence wavelength thereof in the three-dimensional structure of the protein and modifying amino acid residues associated with the structural factor; and a modified fluorescent protein obtained by applying said method. For example, with regard to a GFP-like fluorescent protein from Chiridius poppei, His52 in an α helix-like secondary structure: PFLLSHCMGYGFYHF (α1 47-61) comprising a fluorescent moiety site GYG is replaced with an aromatic amino acid selected from Phe, Tyr and Trp, so as to cause a red shift of the fluorescent peak wavelength; or it is replaced with Ala, Val, Ile, Leu, Gly, Cys, Met, Ser, Thr, or Asp, Asn, Glu or Gln, so as to cause a blue shift of the fluorescence peak wavelength.