An impedance matching device includes a first dielectric substrate; a first transmission line circuit; a first conductive pad which extends toward the first transmission line circuit on the first dielectric substrate to at least partially vertically overlap the first transmission line circuit: a first reference potential layer; and a first matching load which is electrically connected to the first conductive pad and has a first resistance. An area where the first conductive pad vertically overlaps the first transmission line circuit has a size configured such that a load reactance associated with the first transmission line circuit is equal to or less than a predetermined threshold and an absolute value of a difference between a load resistance associated with the first transmission line circuit and the first resistance is equal to or less than a predetermined resistance threshold.