A headlight apparatus includes a headlight unit accommodating headlight bulbs, and a headlight case in which an upper case is detachably mounted to a lower case attached to a stay that is secured to a link type front suspension of a motorcycle with the headlight unit being secured to the lower case. Air intake ports for introducing air into the headlight case are formed on the bottom of the lower case with an exhaust port for discharging air in the headlight case being formed on the rear end of the upper case. A gap is provided between the headlight case and the headlight unit that serves as an introduction passage for introducing air from the intake ports to the exhaust port.