A mounting structure for a curtain airbag device includes: a first pillar (28) constituting a part of a front pillar (26) and extending along a vehicle upper-lower direction; a second pillar (30) constituting another part of the front pillar, disposed on a vehicle rear side at a predetermined interval with respect to the first pillar, and extending along the vehicle upper-lower direction; a transparent member (32) interposed between the first pillar and the second pillar and allowing an outside of a vehicle to be visually recognized from a driver's seat side; a front pillar garnish (34) covering the first pillar and the second pillar from a vehicle cabin side and having a lower end portion protruding along at least one of a vehicle front-rear direction and a vehicle width direction; and a curtain airbag device (44) configured to include a curtain airbag (46) stored along the first pillar or the second pillar, configured to be able to be inflation-deployed in a curtain shape in a vehicle cabin side portion by receiving gas supply during a vehicle collision, and having a front end portion fixed at a position in the first pillar or the second pillar corresponding to the lower end portion of the front pillar garnish.