A photosensitive polymer for a photoresist and a photoresist composition having the same are provided. The photosensitive polymer for a photoresist includes the repeating unit represented by the formula below: ##STR00001## wherein R.sub.1 is a C.sub.1-C.sub.20 hydrocarbon group or a C.sub.1-C.sub.20 hetero hydrocarbon group including at least one hetero atom selected from the group consisting of nitrogen, fluorine and sulfur.