A wireless charger optimized for charging efficiency of portable terminals (e.g., mobile phones) of different sizes has a housing including within it laterally spaced side supports and a bottom support for cradling an inserted portable terminal. The side supports and the bottom support are interlocked for coordinated movement such that the bottom support is moved by a predetermined amount according to movements of the side supports. This arrangement optimizes relative placement of the charger's transmitting coil and the portable terminal's receiving coil.