To accurately measure the concentration of fluid to be measured by ensuring required resolution for measuring the concentration even with a smaller diameter for a tube body for detection.

A microwave transmitting system 28 and a microwave receiving system 29 are disposed opposed to each other on the tube body 1 for detection with a fluid flowing therein. This microwave type concentration meter measures the concentration of fluid based upon a speed variation obtained by propagating microwave through fluid flowing in the tube body 1 for detection. The microwave transmitting system 28 and the microwave receiving system 29 are disposed in such a way that a straight line connecting the microwave transmitting system 28 and the microwave receiving system 29 crosses a tube axis of the tube body 1 for detection with a predetermined angle except a right angle.