Poly (vinyl cinnamate) is a photosensitive polymer having a remarkably resolving power, and it is used for making IC (integrated circuit). Though sensitizing solutions for IC must have various characteristics, researches were made on the content of sodium and the sensitivity after the pre-baking. On the content of sodium, the sensitizing solution obtained in this research contains 0.82 ppm of sodium. On the sensitivity after the pre-baking, it was found that N-acethyl-4-nitro-1-naphthylamine, a new sensitizer, has a good property, and the sensitizing solution resulted in this research holds a high sensitivity after the pre-baking at 130°C for 30 min.