The present invention relates to a novel isolated polypeptide having the ability to export O-phosphoserine (OPS) that is a precursor of L-cysteine, a vector comprising the polynucleotide, an OPS-producing microorganism having enhanced activity of the polypeptide, a method of producing OPS using the microorganism, and a method for preparing cysteine or its derivatives, which comprises reacting OPS, produced by the above method, with a sulfide in the presence of O-phosphoserine sulfhydrylase (OPSS) or a microorganism that expresses OPSS.