A modified polymer body 1 has a polymer body 2 composed of a polymer material containing a carbon-carbon double bond and first binding parts 3 and second binding parts 4 bound to the surface of the polymer body 2. The first binding parts 3 are such that an organic group 6 having a functional group is bound via an isocyanuric acid skeleton 5 to the surface of the polymer body 2. The second binding parts 4 are such that an organic group 7 having a functional group is directly bound to the surface of the polymer body 2 without interposing an isocyanuric acid skeleton 5.