A tire assembly comprising: a tire configured to be mounted on a wheel; a power generating body that is disposed inside the tire; and an electronic device configured to receive supply of power that is output from the power generating body, wherein the power generating body includes a first insulating film having a first surface, a second insulating film having a second surface that faces the first surface and is in contact with the first surface, a first electrode that has conductivity and is in contact with a back surface of the first surface of the first insulating film, and a second electrode that has conductivity and is in contact with a back surface of the second surface of the second insulating film, the power generating body is configured such that a true area of contact between the first surface and the second surface changes according to deformation of the tire, the first insulating film and the second insulating film are configured such that one of the first insulating film and the second insulating film is positively charged and the other of the first insulating film and the second insulating film is negatively charged due to the true area of contact changing, and a voltage is generated across the first electrode and the second electrode due to the first insulating film and the second insulating film being charged, and the power generating body outputs power characterized in that the power generating body is disposed on an inner side surface of a tread portion of the tire, and the tire assembly further comprises a weight that is disposed to the upper surface of the power generating body to press the power generating body such that the first insulating film and the second insulating film approach each other. a tire configured to be mounted on a wheel; a power generating body that is disposed inside the tire; and an electronic device configured to receive supply of power that is output from the power generating body, wherein the power generating body includes a first insulating film having a first surface, a second insulating film having a second surface that faces the first surface and is in contact with the first surface, a first electrode that has conductivity and is in contact with a back surface of the first surface of the first insulating film, and a second electrode that has conductivity and is in contact with a back surface of the second surface of the second insulating film, a first insulating film having a first surface, a second insulating film having a second surface that faces the first surface and is in contact with the first surface, a first electrode that has conductivity and is in contact with a back surface of the first surface of the first insulating film, and a second electrode that has conductivity and is in contact with a back surface of the second surface of the second insulating film, the power generating body is configured such that a true area of contact between the first surface and the second surface changes according to deformation of the tire, the first insulating film and the second insulating film are configured such that one of the first insulating film and the second insulating film is positively charged and the other of the first insulating film and the second insulating film is negatively charged due to the true area of contact changing, and a voltage is generated across the first electrode and the second electrode due to the first insulating film and the second insulating film being charged, and the power generating body outputs power characterized in that the power generating body is disposed on an inner side surface of a tread portion of the tire, and the tire assembly further comprises a weight that is disposed to the upper surface of the power generating body to press the power generating body such that the first insulating film and the second insulating film approach each other.