A vacuum pump of a vehicle for reducing operation noise may include a rotor rotating in a space defined by a housing formed in a pump body at an eccentric position relative to a center of the space, a vane installed to the rotor to rotate eccentrically in the space, and an oil outlet passing through the pump body and formed at a predetermined height above a lower limit of the space such that, when lubricant in the space is discharged in a pressurized state by the vane, the lubricant is not reintroduced back into the space by gravity.