To provide a braking unit of a tucking up curtain which can provide a wide range of braking forces matching not only heavy curtains by increasing the braking forces but also kinds of weight of the curtains by making a braking mechanism inoperative.

A rotation accelerating mechanism 14 for accelerating the rotation of a rotated member 13, and a braking shaft 23 rotated by the rotation accelerating mechanism 14 and making accelerated rotation, are stored in the interior of a casing 12 for holding the rotated member 13 rotated by the rotating shaft 5 of the tucking-up curtain and braking mechanisms 15 and 15 are provided at both ends of the braking shaft 23.