a coil device may be capable of varying the gap of a coil so that several devices may be wirelessly charged simultaneously or a single device may be wirelessly charged with concentrated power . the coil device may include : a case having a reception space and varying a charging area upon a user &# 39 ; s selection ; and a coil part , having , in the reception space of the case , a coil body formed of a wound conductor having a predetermined length . a gap of the wound conductor of the coil body varies as the charging area of the case varies .