An instrument with an IC tag, the instrument comprising: an IC tag having an IC chip and an antenna and being capable of communicating stored information by radio wave in a contactless manner; mounting means configured to mount the IC tag to the instrument; a scale plate provided with scale increments; a pointer to be rotated relative to the scale instruments; and a transparent cover plate that covers the scale increments and the pointer and is supported by a case body by a cover being threadedly engaged with the case body, wherein the mounting means includes: a first member and a second member sandwiching the IC tag, one or both of the members (23a, 23b) are transparent plates which have diameters by which the transparent cover plate can be replaced with the transparent plates (23a, 23b), and the IC tag is disposed between both the members (23a, 23b) so as not to overlap the scale increments and an indicator portion of the pointer in a viewing direction, and a developed plane of the antenna is arranged along the transparent planes (23a, 23b), when the transparent cover plate is replaced, and wherein the antenna is spaced from the scale plate by a first space, the pointer is also spaced from the antenna by a second space, and the antenna is concentrated near the center of the instrument, and is spaced from the cover of the instrument by distances (W1, W2) in the developed plane of the antenna. an IC tag having an IC chip and an antenna and being capable of communicating stored information by radio wave in a contactless manner; mounting means configured to mount the IC tag to the instrument; a scale plate provided with scale increments; a pointer to be rotated relative to the scale instruments; and a transparent cover plate that covers the scale increments and the pointer and is supported by a case body by a cover being threadedly engaged with the case body, wherein the mounting means includes: a first member and a second member sandwiching the IC tag, one or both of the members (23a, 23b) are transparent plates which have diameters by which the transparent cover plate can be replaced with the transparent plates (23a, 23b), and the IC tag is disposed between both the members (23a, 23b) so as not to overlap the scale increments and an indicator portion of the pointer in a viewing direction, and a developed plane of the antenna is arranged along the transparent planes (23a, 23b), when the transparent cover plate is replaced, and wherein the antenna is spaced from the scale plate by a first space, the pointer is also spaced from the antenna by a second space, and the antenna is concentrated near the center of the instrument, and is spaced from the cover of the instrument by distances (W1, W2) in the developed plane of the antenna. a first member and a second member sandwiching the IC tag, one or both of the members (23a, 23b) are transparent plates which have diameters by which the transparent cover plate can be replaced with the transparent plates (23a, 23b), and the IC tag is disposed between both the members (23a, 23b) so as not to overlap the scale increments and an indicator portion of the pointer in a viewing direction, and a developed plane of the antenna is arranged along the transparent planes (23a, 23b), when the transparent cover plate is replaced, and wherein the antenna is spaced from the scale plate by a first space, the pointer is also spaced from the antenna by a second space, and the antenna is concentrated near the center of the instrument, and is spaced from the cover of the instrument by distances (W1, W2) in the developed plane of the antenna. the antenna is spaced from the scale plate by a first space, the pointer is also spaced from the antenna by a second space, and the antenna is concentrated near the center of the instrument, and is spaced from the cover of the instrument by distances (W1, W2) in the developed plane of the antenna.