AbstractThe problem of electromagnetic wave propagation in tunnels with branches and bends, such as those that would be found in an underground shopping center, has been analyzed with the finite‐volume/time‐domain (FV‐TD) method. The FVTD method is based on difference equations discretized by a volume integration of Maxwell's equations for arbitrarily small polygonal cells. In this method, the medium constants within the infinitesimal cell are constant and their values differ from cell to cell. Therefore, this method can easily handle the boundary value problem with an arbitrary shape that contains inhomogeneous media. In homogeneous media, the FVTD method and the finite‐difference/time‐domain (FDTD) method are equivalent in the Descartes coordinate system. In one application of the FVTD method, numerical calculations were made for tunnel structures that are typically difficult to analyze. To prove the usefulness of the FVTD method, a microwave simulation experiment was done. The numerical and experimental values were shown to agree well.