[Problem] To provide a resin overcap provided with an IC tag that can be used as an overcap being fitted onto a metal cap and having an IC tag that is so provided that the transmission and reception of signals will not be disturbed by the metal cap.[Means for Solution] A resin overcap used being fitted onto a metal cap, comprising a top panel and a cylindrical side wall hanging down from the circumferential edge of the top panel and in which the metal cap is fitted, wherein a step or a protrusion is formed on an upper portion on the inner surface of the cylindrical side wall to prevent the upward motion of the metal cap fitted in the cylindrical side wall, and an IC tag provided with an IC chip is mounted on the top panel in a manner of maintaining a predetermined distance D to a top plate of the metal cap fitted into the cylindrical side wall.