An electromagnetic field strength calculator calculates currents flowing through an electric circuit device which is an object of analysis by means of the moment method, and calculates and displays the strength of an electromagnetic field radiated from the electric circuit device from the calculated currents. In this calculator, a grid setup unit partitions a plane of a model representing the circuit device with a grid of lines having specified spacing. Next, a current calculation unit calculates currents at grid intersections or points within areas partitioned by the grid, on the basis of currents flowing through an element of the model of the circuit device calculated by means of the moment method. The currents thus calculated are displayed on a display by a current display unit. This allows a current at a point in the electric circuit device to be visually displayed in a form easy to understand.