Breather device of engine

abcaA breather device comprises a breather chamber provided in a valve arm chamber arranged above a cylinder head of an engine. In the breather chamber, blow-by gas including oil mist is separated into oil component and gas component, and the oil mist is removed from the blow-by gas. The interior of the breather chamber is alternately divided into plural horizontally juxtaposed rooms by a partition extended from a bottom surface of the breather chamber and a partition extended from a ceiling surface of the breather chamber. Plural oil trap members for trapping oil mist in the blow-by gas are arranged in the breather chamber. Especially, the oil trap member arranged at a blow-by gas inlet of the breather chamber is held by a holder made separately from members forming the valve arm chamber.