Fluorescent nucleotides useful for labeling nucleic acids which are represented by the formula: X--Y--Z wherein X represents a residue of natural or non-natural nucleotide and the like and binds to Y at a basic moiety of the residue; Y represents a divalent bridging group or a single bond; Z represents a monovalent group derived from a compound represented by the formula (I) wherein R.sup.1 to R.sup.4 represent an alkyl group; V.sup.1 to V.sup.6 represent a hydrogen atom or a substituent; L.sup.1 to L.sup.7 represent a methine group; W represents an oxygen atom, a sulfur atom, --C(R.sup.3)(R.sup.4)-- or --N(R.sup.5)-- wherein R.sup.3 to R.sup.5 represents an alkyl group; Q represents a nitrogen atom or --C(V.sup.7)-- wherein V.sup.7 represents a hydrogen atom or a monovalent substituent; M represents a counter ion; m represents a number required to neutralize the charge of the molecule; s, t and u represent 0 or 1 or the like, and binds to Y at a reactive group existing in R.sup.1 or R.sup.2 ##STR00001##