There is provided a photoresist including (a) a resin composed of a polymer having a compound represented with the following general formula �1! within a structural unit thereof, and (b) a photo acid generator. ##STR1## wherein R.sup.1 represents a hydrogen atom, R.sup.2 represents a divalent hydrocarbon group including a bridged cyclic hydrocarbon group and having a carbon number in the range of 7 to 13 both inclusive, R.sup.3 and R.sup.4 represent a hydrocarbon group having a carbon number of 1 or 2, and R.sup.5 represents one of (a) a hydrocarbon group having a carbon number of 1 to 12, (b) a hydrocarbon group having a carbon number of 1 to 12 and replaced with an alkoxy group having a carbon number of 1 to 12, and (c) a hydrocarbon group having a carbon number of 1 to 12 and replaced with an acyl group having a carbon number of 1 to 13. The above mentioned photoresist produces no extra polymer by side reaction. Thus, the photoresist makes it possible to form a fine pattern without resist residue, and has superior thermal stability.