A collapsing and securing device of a lateral blind includes a lateral blind such as a winding blind, a Roman blind, or a cloth blind, and a number of positioning members fixed at least on one surface of the window curtain, and the positioning members can temporarily adhere, stick or attract each other to secure the lateral blind at one of many collapsed position in case the lateral blind is manually wound up, without using pull ropes with a pool as used in a conventional lateral blind for preventing potential dangers involved in conventional lateral blinds. The collapsed lateral blind can be expanded down manually with easiness and quickness, with the temporarily adhered, stuck or attracted together positioning members separated from one another with easiness.