A venetian blind includes a covering unit, and a cord-winding device. The covering unit includes a plurality of slats and two lifting cords. The cord-winding device includes a casing fixed on the headrail, a plurality of spring-surrounding members disposed rotatably within the casing, a plurality of co-rotatable gears sleeved respectively and fixedly on the spring-surrounding members, and a spiral spring disposed within one of the spring-surrounding members. The spiral spring is disposed within one of the spring-surrounding members, and has two ends fastened respectively to the casing and the one of the spring-surrounding members. Each of the lifting cords has two ends connected respectively to the bottom rail and a corresponding one of the spring-surrounding members. The spiral spring imparts a spring force to substantially balance the total weight of the bottom rail and the covering unit so as to maintain the bottom rail at any position.
