To provide a take-up shaft supporting device of a roll blind capable of easily mounting the take-up shaft of the roll blind to a supporting bracket and, at the same time, surely holding a take-up shaft on the supporting bracket.

For the take-up shaft supporting device of the roll blind having a supporting hole 13 for supporting the axial center 15 of the take-up shaft of a screen 4 incapable of being moved in the direction of the axis on the supporting bracket 1a, having an opening section 14 capable of inserting the axial center 15 thereinto in the supporting hole 13, having a first holding means 17 for holding the axial center in the supporting hole 13 by closing the opening section 14 and, at the same time, having an energizing means 24 for elastically maintaining the first holding means 17 in a closed position of the opening section, the first holding means 17 is provided to the direction at right angles to the supporting bracket 1a in a rotatable manner, and a projected piece 19 capable of being held on the supporting bracket 1a in the closed position is provided to the first holding means 17.