Abstract: Methods and apparatus are disclosed for sensing opening of an electronic seal device. According to one embodiment, the electronic seal device includes a T-shaped bolt unit including a protrusion formed to protrude from a first side thereof at a predetermined thickness to provide directionality, the bolt unit transmitting unique data as a Radio Frequency (RF) signal; and an electronic circuit unit including a groove formed in the wall of a hole to provide directionality so that part of the shank of the bolt unit is inserted into and engaged with the hole to a predetermined depth, and a drainage hole is formed in a lower portion of the electronic circuit unit, the electronic circuit unit transmitting/receiving RF signals to/from the bolt unit.