We have analyzed the band-stopping characteristic of non-metal periodic structures for electromagnetic wave in a microwave region. The target frequencies are 2.4 and 5 GHz bands, which are popularly used in wireless LAN in Japan. There are two types of periodic structure in this article. One is the multilayer slab (a 1D photonic crystal) and the other is the square lattice of dielectric columns (a 2D photonic crystal). The finite-difference time-domain (FDTD) method is employed for the numerical calculation. Frequency and spatial characteristics of band-stopping are shown as numerical examples.