A mounting structure for a curtain airbag device includes: a first pillar extending along a vehicle upper-lower direction; a second 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 interposed between the first pillar and the second pillar; a front pillar garnish covering the first pillar and the second pillar 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 configured to include a curtain airbag, configured to be inflation-deployed in a curtain shape in a vehicle cabin side portion, 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.