A method for manufacturing a semiconductor device comprising, forming a first photoresist pattern by exposing and then developing a first photoresist film formed on a substrate, irradiating the first photoresist pattern with UV light to cure its surface, forming a second photoresist film so as to cover the substrate and the first photoresist pattern, forming a second photoresist pattern and performing ion implantation in the substrate using the second photoresist pattern. The second photoresist pattern is not subjected to UV irradiation after the second photoresist film has been developed and before the ion implantation is performed, or is irradiated with the UV light, after the second photoresist film has been developed and before the ion implantation is performed, under a reduced condition relative to that for the first photoresist pattern.