We describe a method for simulating an electromagnetic induction type wireless power transmission (WPT) device. This simulator was based on the finite-difference, time-domain method. To reduce computation time, two graphics processing units (GPUs) were used as accelerators for the electromagnetic field computation. The first GPU calculated the electromagnetic field for the non-resonance state, and the second GPU calculated the field for the resonance state. Only two physical quantities needed to be exchanged between the two GPUs: self-inductance and the magnetic coupling coefficient. Capacitors and a load resistance were virtually connected to the coils as lumped elements. The experimental and simulation results were in good agreement. It is expected that a transient response analysis of WPT devices will become possible in the future using this simulation architecture.