The measuring device (100, 200, 300) includes an irradiation unit (10, 10a, 10b) that irradiates light to the fluid, a light receiving unit (21) that receives light scattered by the fluid, and a flow rate or flow velocity of the fluid. The acquisition part (23) which acquires the fluid information to show, and the control part (30) which controls an irradiation part based on fluid information are provided.計測装置（１００、２００、３００）は、流体に光を照射する照射部（１０、１０ａ、１０ｂ）と、流体によって散乱された光を受光する受光部（２１）と、流体の流量又は流速を示す流体情報を取得する取得部（２３）と、流体情報に基づいて、照射部を制御する制御部（３０）と、備える。
