Abstract: An optical integrator, which may be for a DLP system projector, is provided and includes an integral rod, a rod storage case, a resin housing, and a heat sink. The rod storage case includes an optical tube and covers. A sealed room formed between the optical tube and the rod outer surface of the integral rod is filled with a cooling liquid. A boss is formed on the top surface of the rod storage case. A penetration hole is formed in the resin housing and a penetration hole is formed in the heat sink. The rod storage case and the heat sink are coupled together so as to pinch the resin housing. The heat of the cooling liquid in the sealed room is dissipated from the resin housing through the boss and the heat sink. It is thus possible to efficiently cool the integral rod.