The present disclosure relates to a dust-proof caster assembly including a caster having a peripheral annular recess disposed thereon and a casing having a corresponding annular peripheral flange which can be fitly engaged with the annular recess when the caster and the casing are assembled together, thus effectively preventing dust or fragmental threads in a textile factory from getting into the fissure between the wheel hub and the bearing, improving the operation of the caster and enhancing the longevity thereof.