To suitably prohibit use of an electric appliance provided with an attachment plug, for example.

The attachment plug sealing device (1) includes a casing (2) for housing at least a part of components of the attachment plug sealing device, and female insertion holes (31, 32) formed on the casing and corresponding to male terminals provided on the attachment plug. The attachment plug sealing device is further provided with an engagement means (41) for switchably engaging with an engagement hole formed on the male terminal, and a locking means (5) for locking while the engagement means is being engaged with the engagement hole of the attachment plug.