An internal combustion engine (1) includes: a cylinder head (2); an oil feed passage (16); a camshaft (3); a vacuum pump (35) that has a rotor (36) and a housing (42), with a negative-pressure chamber defined by the rotor (36) and the housing (42) being connected to the oil feed passage (16), and is configured to generate negative pressure inside the negative-pressure chamber as the rotor (36) rotates; a hydraulic lash adjuster (21) connected to the oil feed passage (16); and a branch passage (76) branched from the oil feed passage (16). An open hole (73) open to the atmosphere is provided at a leading end of the branch passage (76), and oil is fed through the open hole (73) to the camshaft (3) while the internal combustion engine (1) is in operation, and air is introduced through the open hole (73) into the vacuum pump (35) while the internal combustion engine (1) is stopped.