A breather device for an engine, in which a predetermined gap (α) is formed between an outer surface of a breather chamber (26) placed inside the head cover (13) and an inner surface of a head cover (13). The gap (α) functions as a heat insulation space even if outdoor air temperature drops, and this prevents freezing of blow-by gas in the breather chamber (26). In addition, a blow-by gas entrance (30) formed in a wall surface of the breather chamber (26) is opened at a position facing the inner surface of the head cover (13). This not only enhances the degree of positioning freedom for the blow-by gas entrance (30) to a levelhigher than that of a case where the blow-by gas entrance (30) is opened at a lower surface of the breather chamber (26) but also allows the gap (α) between the breather chamber (26) and the head cover (13) to exhibit a good oil separation effect, preventing the entry of oil into the breather chamber (26).
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