In order to provide a small size antenna where excellent antenna properties can be stably gained, a frequency adjustment is easy and a simple measurement is possible, according to the present invention, a small size antenna formed of a conductor of at least two adjoining surfaces of a base in rectangular parallelepiped form made of dielectric ceramics is characterized in that: a step is made of a flat portion parallel to one surface of the two adjoining surfaces and an inclining portion located between the one surface and the flat portion, in a corner portion of the two surfaces on which the conductor is formed; the width of the flat portion is 0.08 mm or less; and a border portion between the flat portion and the other surface of the two adjoining surfaces is a curve having a curvature radius R of 0.03 mm to 0.2 mm.