To provide a variable-capacity capacitor and a high-frequency component which are excellent in their power resistances, by giving to the capacitor a capacitor forming region whose shape reduces the concentration of the electric field applied to the region.

With respect to the variable-capacity capacitor, first and second lower electrode layers 22a, 22b are so formed adhesively on a supporting substrate 21 as to separate them from each other, and a dielectric layer 23 whose dielectric constant is varied by applying an external voltage to it is so formed adhesively that it bestrides the gap between the first and second lower electrode layers 22a, 22b, and further, a first upper electrode layer 24a is so formed on the first lower electrode layer 22a and on the dielectric layer 23 that a capacitor forming region 10a opposes via the dielectric layer 23 to the second lower electrode layer 22b. In the variable-capacity capacitor, the shape of the end of the first upper electrode layer 24a whereon the capacitor forming region 10a is formed has the shape comprising at least a portion of a circle.