A curtain airbag device mounting structure includes: a first pillar forming a part of a front pillar and extends substantially along a vehicle height direction; a second pillar forming another part of the front pillar, the second pillar being disposed on a rear side of a vehicle relative to the first pillar at a predetermined distance from the first pillar and extending substantially along the vehicle height direction; a transparent member bridged between the first pillar and the second pillar; and a curtain airbag device including a curtain airbag stored along a roof side rail and the second pillar, the curtain airbag being configured to inflate and deploy in a curtain-like fashion over a side portion of a cabin of the vehicle in case of a collision of the vehicle.