Provided is a roll unit to be dipped in a surface treatment liquid of a copper foil, wherein a bearing box for housing a roil shaft is configured from two bearing boxes that are divisible, one of the bearing boxes is configured from a roll-side bearing box arranged on a roll main body-side and the other bearing box is configured from a shaft end-side bearing box arranged on the shaft end-side of the roll, a shaft sleeve covering an outer periphery of the roll shaft is provided in the roll-side bearing box and an oil seal is provided along an outer periphery of the shaft sleeve, and a bearing for rotatably supporting the shaft is disposed in the shaft end-side bearing box. Specifically, the present invention provides a roll unit to be used in electrochemical surface treatments such as roughening treatment, rust prevention treatment, and oxidized surface treatment (blackening treatment) to be continuously performed on a surface of a rolled copper foil or an electrolytic copper foil, and which is capable of inhibiting the abrasion and corrosion of the roll shaft of such roll unit by controlling the corrosion caused by the infiltration of the treatment liquid, and which enables the simple replacement of the bearing box, bearing, and other components.