A radiation sensitive dielectric constant changing composition comprising (A) a decomposable compound, (B) a nondecomposable compound, (C) a radiation sensitive decomposer and (D) a stabilizer.The composition allows its dielectric constant to be changed by a simple method, has a sufficiently large difference between its changed dielectric constant and its original dielectric constant and can provide a dielectric constant pattern and an optical material which are stable regardless of their use conditions.