An object of the present invention is to provide a niobium sintered body free of reduction in the CV value, a niobium powder for use in the manufacture of the niobium sintered body, and a capacitor using the niobium sintered body. A niobium powder of the present invention has niobium and tantalum, where the tantalum is present in an amount at most of about 700 ppm by mass. A sintered body and a capacitor each is manufactured using the niobium powder.