An antenna circuit constituent body for an IC card/tag, comprising: a base material formed of a resin film; and an antenna circuit pattern layer formed on one surface of the base material and constituted of a conductive body including metal as a main component, the antenna circuit pattern layer including: a first circuit pattern layer part and a second circuit pattern layer part electrically connected to each other; and a third circuit pattern layer part formed on one surface of a region of the base material between the first and second circuit pattern layer parts (103 and 104), the antenna circuit constituent body for an IC card/tag further comprising: an insulating layer formed so as to extend from an upper part of the first circuit pattern layer part, via an upper part of the third circuit pattern layer part, to an upper part of the second circuit pattern layer part; and a conductive layer formed on the insulating layer so as to bring the first circuit pattern layer part and the second circuit pattern layer part into conduction, characterized in that the insulating layer has a plurality of inclined end surfaces or a split-level portion on each of the first circuit pattern layer part and the second circuit pattern layer part, each of the end surfaces being inclined by an angle greater than or equal to a base material formed of a resin film; and an antenna circuit pattern layer formed on one surface of the base material and constituted of a conductive body including metal as a main component, the antenna circuit pattern layer including: a first circuit pattern layer part and a second circuit pattern layer part electrically connected to each other; and a third circuit pattern layer part formed on one surface of a region of the base material between the first and second circuit pattern layer parts (103 and 104), a first circuit pattern layer part and a second circuit pattern layer part electrically connected to each other; and a third circuit pattern layer part formed on one surface of a region of the base material between the first and second circuit pattern layer parts (103 and 104), the antenna circuit constituent body for an IC card/tag further comprising: an insulating layer formed so as to extend from an upper part of the first circuit pattern layer part, via an upper part of the third circuit pattern layer part, to an upper part of the second circuit pattern layer part; and a conductive layer formed on the insulating layer so as to bring the first circuit pattern layer part and the second circuit pattern layer part into conduction, characterized in that the insulating layer has a plurality of inclined end surfaces or a split-level portion on each of the first circuit pattern layer part and the second circuit pattern layer part, each of the end surfaces being inclined by an angle greater than or equal to an insulating layer formed so as to extend from an upper part of the first circuit pattern layer part, via an upper part of the third circuit pattern layer part, to an upper part of the second circuit pattern layer part; and a conductive layer formed on the insulating layer so as to bring the first circuit pattern layer part and the second circuit pattern layer part into conduction, characterized in that the insulating layer has a plurality of inclined end surfaces or a split-level portion on each of the first circuit pattern layer part and the second circuit pattern layer part, each of the end surfaces being inclined by an angle greater than or equal to