To provide a method of evaluating an electromagnetic wave transmission structure which enables the analysis of the electromagnetic condition in a scale of the body of an aircraft, taking electromagnetic wave characteristics of a heterogeneous and complicatedly shaped structure into consideration.

The internal electric field of an electromagnetic wave transmitting structure letting electromagnetic waves to pass through is calculated according to a three-dimensional volume integral expression. The time-averaged value of the normal component of the complex Poynting vector at an observation point on an observation surface set near the transmission structure is calculated, based on the internal electric field. The reflection coefficient and the transmission coefficient of the transmission structure are calculated, based on the time- averaged value. Calculated values of the reflection coefficient and the transmission coefficient of the transmission structure at a plurality of observation points are averaged to obtain values of the reflection coefficient and the transmission coefficient of the entire transmission structure.