To provide an anti-theft device of packed merchandise configuring a blister pack.

The anti-theft device includes a restraint system 1 having a cable 66 laid to packed merchandise 60 and an anti-theft tag 24. An upper fixing tool 64 and a lower fixing tool 65 installed in the cable 66 are configured to hold an upper edge part 60a and a lower edge part 60c. The cable 66 is configured to lay an upper sash part 79 from the upper fixing tool 64 to both side edge parts 60b and 60b, and to lay a lower sash part 80 from a lower fixing tool 65 to the both side edge parts 60b and 60b, and to connect them by a connection part 81 on the rear face of the packed merchandise 60, and a free end part 82 extended on the rear face of the packed merchandise 60 from either the upper sash part 79 or the lower sash part 80 is restrained by the restraint system 1. The restraint system 1 includes locking means for locking restraint means 5, and the restraint means 5 is unlocked when it is unlocked by an unlock key.