Abstract: An opening detection sheet to be attached to a packaging material includes a metal layer, an IC, an insulating layer, and a first adhesive layer. The metal layer is releasable from the packaging material and includes a slit. The IC is mounted on the metal layer so as to cover at least a portion of the slit and for communicating with an external device. The insulating layer is disposed on an opposite side from the IC with respect to the metal layer. The first adhesive layer is bonded to the insulating layer on an opposite side from the metal layer so as to be bonded to the packaging material.