To perform a one-touch, speedy, and precise measurement of a powdery or granular matter by rotating a cylindrical body adjustable in volume by the operation of a knob to measure the matter.

A measuring instrument used for measuring domestic detergent, for example, has an outer cylindrical body 2 having an outlet port 5 and an inlet port in the front and rear, an inner cylindrical body having a common hole 6 for taking out and in and a measuring space 7, and a measuring part 10 integrated with a driving shaft 8. The measuring part 10 is inserted to the inner cylindrical body, a driving bearing part 9 is mounted thereon, and inserted to the outer cylindrical body 2, a lid 13 is put thereon, and a knob 11 is fixed to one end of the driving shaft 8. The measuring instrument is set to a box containing a measuring matter to make the measuring matter flow thereto, and the measuring part 10 is fitted to a measuring scale 15 by the knob 11 to set the quantity of the measuring matter in the measuring space 7. When the knob 11 is rotated, a fixed quantity of the measuring matter is supplied through the outlet port 5.