An indicator for emitting a light is provided, the indicator comprising a plate-shaped member which has a stress-concentrating section for causing stress concentration, and a stress-transmitting section for transmitting, to the stress-concentrating section, a stress generated due to an external force; wherein the stress-concentrating section is provided with a stress light-emitting section which is formed of a stress light-emitting material that emits the light in response to a change of the stress. The stress-concentrating section can be arranged such that the stress-concentrating section is not hidden by a finger when the force is applied to the indicator with the finger or the like. The visibility of the light emission can be secured by the light emission effected by the stress light-emitting material applied to the stress-concentrating section which is not hidden by the finger.