The invention relates to a device (1) for winding up and unwinding raising cords of a screen, comprising: an elongate housing (2); a shaft (3) intended for rotation in the housing; a number of winding rollers (4) which are coaxially mountable on the shaft for winding up and unwinding the raising cords (5) and which are adapted for releasable fastening of the raising cords; a number of winding roller holders (6) for bearing-mounted support of the winding rollers, which winding roller holders are adapted to be received in the housing. The device further comprises a number of blocking elements (10), each arranged on one of the winding rollers, for blocking one of the degrees of freedom of movement of the winding rollers, wherein each blocking element is movable between an assembly position, in which the respective winding roller is blocked against rotation, and a position of use in which the respective winding roller is blocked against translation, wherein the blocking elements are adapted for releasable fastening of one of the raising cords.