An engine includes an EGR apparatus which refluxes a portion of exhaust gas from an exhaust manifold to an intake manifold as EGR gas. A differential pressure sensor detects a differential pressure between intake pressure of the intake manifold and exhaust pressure in the exhaust manifold. The differential pressure sensor is mounted on a head cover which covers an upper portion of a cylinder head. An intake pressure taking-out passage which is in communication with the intake manifold is formed in the cylinder head. An intake pressure introducing passage which is connected to the differential pressure sensor is formed in the head cover. The intake pressure taking-out passage and the intake pressure introducing passage are in communication with each other.