A polymeric fluorescent substance exhibiting strong visible fluorescence in solid state. The substance has a polystyrene reduced number-average molecular weight of 110³ to 110⁸, and contains repeating units represented by formula (1),

—Ar₁—(CR₁CR₂)_m—  (1)

in the formula, Ar₁ represents an arylene group having a specific substituent. By using the polymeric fluorescent substance, a high performance polymer LED can be prepared easily.