A slotted patch antenna includes a dielectric substrate, a radiation electrode which is provided on a major surface of the dielectric substrate, and a ground conductor which is disposed on a surface that is opposite to the major surface. The radiation electrode is formed with a slots having at least one of a meandering portion, a curve portion, or a folded portion. An external shape of the radiation electrode is a square, and totally two pairs of slots are formed inside the square, each of the slots being along respective sides of the square. Each of the slots is arranged so as to be line-symmetrical with respect to an axis of symmetry that is parallel with one of the sides of the square and passes through a center of the square, and to be point-symmetrical with respect to the center of the square.