A trigger signal generating device outputs a trigger signal activating an IC tag. The trigger signal generating device includes first and second trigger coils placed at a predetermined separation distance and each having predetermined magnetic field intensity distribution. Each of the first and second trigger coils includes attenuating means for attenuating intensity of a magnetic field generated by the first and second trigger coils to a predetermined level that allows the ID tag to detect trigger IDs of the first and second trigger coils on a side on which the first and second trigger coils are provided, and that does not allow the ID tag to detect the trigger ID of the first trigger coil on an opposite side to the side on which the first and second trigger coils are provided.