A curtain bead chain fixing device includes a bead chain guide way through which a bead chain as a pull cord for controlling a curtain is extended and thereby becomes connected to the fixing device, and an elastically movable interfering element being normally pushed into the bead chain guide way to interfere with the free movement of the bead chain in and along the bead chain guide way. When the fixing device is adequately mounted to a wall surface according to specified installation procedures, the interfering element is forced out of the bead chain guide way to release the bead chain therefrom. Therefore, a user of the curtain is urged and guided to adequately mount the fixing device to hold the bead chain in place, and undesired accidents caused by a swinging bead chain can be avoided.