The present invention relates to a blind cord safety device. The present invention comprises: a corrugated tube provided to have a pipe shaped body to enable a blind cord to penetrate an inside of which a length is extended or shrunk in a longitudinal direction of the blind cord; a first module connected to a lower end part of the corrugated tube wherein an end portion of the blind cord is hung by the inside; and a second module attached and detached from the first module on an upper portion of the first module while having the corrugated tube therebetween to enable the corrugated tube to be folded. When the second module is lifted upwards with respect to the first module, the corrugated tubes are provided to have a different thickness to automatically be unfolded by elasticity.
