An optical apparatus includes a heat sink radiating the image sensor, a cooling fan unit configured to cool the heat sink, and a first lens barrel including a hollow portion configured to guide light to the image sensor. The first lens barrel holds the cooling fan unit and house the holder unit movably in the hollow portion in an optical axis direction of the image pickup optical system. The holder unit includes a first inlet and a first outlet. The first lens barrel includes a second inlet for taking in external air and a second outlet for exhausting the external air taken in through the second inlet. The first inlet is connected to the second inlet and the first outlet is connected to the second outlet when the holder unit is positioned in the hollow portion of the first lens barrel.