A headlight unit having a virtual pivot center provided at a position different from a supported position to a vehicle body. Two, upper and lower headlight supporting portions spaced apart from each other are provided at a rear portion of a headlight unit The upper headlight supporting portion on each side includes a guide shaft formed on a support member of a radiator cover and a groove formed on an upper base portion of the headlight unit. The lower headlight supporting portion on each side includes an elongated hole formed through the support member of the radiator cover and a bolt threadedly engaged with a lower base portion of the headlight unit. The guide shaft and the bolt slide in the groove and the elongated hole, respectively, for performing the swing motion of the headlight unit about the virtual pivot center C to perform an adjustment of an optical axis.