An engine (E) of a saddle-riding type vehicle has an engine case that is substantially L-shaped by a cylinder block (42) being protruded upward from an upper face of a front portion of a crank case (40). An air cleaner (55) is disposed rearwardly of the cylinder block (42) and above the crank case (40). An outlet (72) through which blow-by gas (G) in the engine (E) is discharged is formed in the rear portion of the cylinder block (42). A case body (84) of the air cleaner (55) has a blow-by gas introduction port (86) through which the blow-by gas (G) is introduced into the air cleaner (55). The outlet (72) of the cylinder block (42) and the blow-by gas introduction port (86) of the case body (84) are connected by a connecting pipe (90). The blow-by gas introduction port (86) is disposed close to the cylinder block (42).