This invention provides a chemically amplified photosensitive resin composition suitable for forming a thick film and a super thick film, which has high sensitivity, high film residual properties, good coating properties, high resolution and a good pattern shape, and which gives a pattern excellent in heat resistance, in a photosensitive resin composition requiring the formation of a thick resistpattern film such as in the formation of a magnetic pole of a magnetic head or of a bump. A chemically amplified photosensitive resin composition including an alkali soluble novolak resin (A), a resinor compound (B) which in itself is insoluble or slightly soluble in alkali, but becomes soluble in alkali by the action of an acid, that is acid generating agent (C), and a photosensitizing agent (D)containing a quinonediazide group, as well as, if necessary, an alkali soluble acrylic resin (E) and a crosslinking agent (F) for improving film quality.