A measurement device includes a sensing portion and a measuring portion. The sensing portion contains at least a fluorescent material whose emitting of fluorescent light ceases due to an action of a radioactive beam. The measuring portion measures a radiation quantity of the radioactive beam, with which the sensing portion is irradiated, based on an amount of decrease in the intensity of the fluorescent light emitted by the fluorescent material contained in the sensing portion when the radioactive beam acts on at least a portion of the fluorescent material. The fluorescent light is emitted due to irradiation of the fluorescent material by an excitation source.
