A polymeric fluorescent substance has a prolonged service life and high luminescence brightness. The substance also has excellent thermal stability and good practicality. The polymeric fluorescent substance is adapted for emission of visible fluorescence in a solid state, and includes at least one type of repeating units represented by a specified chemical formula (1). In addition, the substance has a number average molecular weight of 10.sup.3 to 10.sup.8 as determined using polystyrene as a standard. A process for producing the polymeric fluorescent substance, and an organic EL element using the polymeric fluorescent substance are also provided.