An IC tag in which precision reduction is suppressed and which is compact and manufactured easily, and a manufacturing method of IC tag are provided. The IC tag has: antennas disposed on one surface of a substrate; a capacitor which includes a dielectric and first and second electrodes disposed on one surface of the substrate, and in which an electrostatic capacitance changes irreversibly corresponding to changes in ambient environment; and an IC chip which detects the electrostatic capacitance of the capacitor via a pair of external terminals to which the first and second electrodes are respectively connected, and wirelessly transmits information based on a detection result via the antennas.