A foreign object detector includes a detection coil; a transmitting circuit generating an unbalanced signal; a balanced-to-unbalanced transformer transforming the unbalanced signal supplied from the transmitting circuit to a balanced signal; and detection circuit detecting a foreign object by sensing a change in frequency characteristic of reflected power that is a power component reflected by the detection coil. The foreign object detector detects a foreign object while preventing a wire between the detection coil and the detection circuit from functioning as a linear antenna even if the wire is long.