A multi-cylinder diesel engine which has a common rail (3) extending in a fore-and-aft direction and is disposed above an intake manifold (2), and an engine cooling fan 4 is disposed at the front of the engine. A air intake portion (6) of the intake manifold (2) is disposed laterally outwardly of the common rail 3 and opposite a head cover (5). The common rail 3 is disposed in the path of cooling air blown by the engine cooling fan (4).