Front structure of an engine designed to arrange a plurality of auxiliary devices (38, 39, 40) beside an intake-side of an engine body and to drive the auxiliary devices (38, 39, 40) by a crankshaft through an auxiliary-devices driving belt comprising: a balancer-unit in an oil pan; a balancer-unit sprocket on the balancer-unit; a balancer-unit driving chain which is so wound around the balancer-unit sprocket that the balancer-unit is driven by a crankshaft; a pair of camshafts (11a, 12a) disposed on a cylinder head; an intermediate shaft through which drive force is transmitted from the crankshaft to the camshafts (11a, 12a); and a pair of upper and lower camshaft driving chains (14, 20) adapted to couple the crankshaft to the camshafts (11a, 12a), characterized by: the lower camshaft driving chain which is arranged behind the upper camshaft driving chain; a chain cover which covers a front side of the chains (14, 20, and 26) and has upper and lower front parts formed such that the lower front part is depressed toward a cylinder block relative to the upper front part in a longitudinal direction of the engine along with respective front surfaces of the chains (14, 20, and 26); an auxiliary-devices driving belt disposed in front of the chain cover; and by a cantilevered arm holding a belt tensioner at a free end thereof, associated with the auxiliary-devices driving belt, and is disposed in front of the chain cover in such a manner as to overlap with a looped area formed by the lower camshaft driving chain in front view of the engine. a balancer-unit in an oil pan; a balancer-unit sprocket on the balancer-unit; a balancer-unit driving chain which is so wound around the balancer-unit sprocket that the balancer-unit is driven by a crankshaft; a pair of camshafts (11a, 12a) disposed on a cylinder head; an intermediate shaft through which drive force is transmitted from the crankshaft to the camshafts (11a, 12a); and a pair of upper and lower camshaft driving chains (14, 20) adapted to couple the crankshaft to the camshafts (11a, 12a), characterized by: the lower camshaft driving chain which is arranged behind the upper camshaft driving chain; a chain cover which covers a front side of the chains (14, 20, and 26) and has upper and lower front parts formed such that the lower front part is depressed toward a cylinder block relative to the upper front part in a longitudinal direction of the engine along with respective front surfaces of the chains (14, 20, and 26); an auxiliary-devices driving belt disposed in front of the chain cover; and by a cantilevered arm holding a belt tensioner at a free end thereof, associated with the auxiliary-devices driving belt, and is disposed in front of the chain cover in such a manner as to overlap with a looped area formed by the lower camshaft driving chain in front view of the engine. the lower camshaft driving chain which is arranged behind the upper camshaft driving chain; a chain cover which covers a front side of the chains (14, 20, and 26) and has upper and lower front parts formed such that the lower front part is depressed toward a cylinder block relative to the upper front part in a longitudinal direction of the engine along with respective front surfaces of the chains (14, 20, and 26); an auxiliary-devices driving belt disposed in front of the chain cover; and by a cantilevered arm holding a belt tensioner at a free end thereof, associated with the auxiliary-devices driving belt, and is disposed in front of the chain cover in such a manner as to overlap with a looped area formed by the lower camshaft driving chain in front view of the engine.