Electrical vehicles (EVs) attract increasing attention as environmental conservation becomes ever more important. Wireless power transfer (WPT) is considered to make EVs more popular; however, the WPT must achieve high efficiency, even when there are wide variations in the load impedance and in the offset and the gap between the primary and secondary coils. We propose a new method of designing an impedance matching network (IMN) that realizes the circuit characteristics of an ideal transformer. The proposed method achieves high efficiency at any point within wide variations of offset and gap and load impedance, as confirmed by experiments.