To provide a positive type photoresist composition less liable to cause development defects in the production of a semiconductor device, excellent in adhesion on an inorganic antireflection film and excellent also in exposure margin (in particular, exposure margin in the case of isolated lines), sensitivity change with age, etc.

The positive type photoresist composition contains (A) a resin containing repeating structural units with norbornene and repeating structural units containing a specified alicyclic hydrocarbon structure and having a velocity of dissolution in an alkali developing solution increased by the action of an acid and (B) a compound which generates the acid when irradiated with active light or radiation.