An ozone gas generator includes a first electrode portion that includes a first electrode, and a second electrode portion that faces the first electrode portion, is disposed with a predetermined interval at which discharge between the first electrode portion and the second electrode portion is possible, and includes a second electrode, in which at least one of the first electrode portion and the second electrode portion includes a dielectric that is provided on a surface of the first electrode or the second electrode on sides facing each other, and at least one of the first electrode portion and the second electrode portion includes a layer that is provided on at least a portion of the surface of the first electrode or the second electrode on the sides facing each other, or the dielectric, and includes at least one of a metal or a metal compound, and the first electrode portion and the second electrode portion are configured such that accuracy of an interval between surfaces facing each other is ±3% or more and ±50% or less.