PURPOSE: To completely wash an electromagnetic relay in a cleaning liquid and to release the relay from a hermetically sealed state when in use to enable release of heat by releasing inner expanding air from a vent hole provided in advance when sealing a block and a cover together using a thermosetting adhesive, and then hermetically sealing the hole, the block and the cover constituting the relay.

CONSTITUTION: A block 2 is formed of an insulating material such as synthetic resin and takes the shape of a flat plate and an electromagnetic relay main body 1 is placed thereon with a terminal 1a being passed through the block 2. A cover 3 is similarly formed of synthetic resin and the side of the cover 3 which makes contact with the block 2 is opened and a protrusion 3b in the form of a chimny is mounted via a vent hole 3d on the upper surface of the cover 3 which is opposite to said side, the vent hole 3d being provided through the upper surface. The bottom surface of the cover 3 and the upper surface of the block 2 are heated and hardened using a thermosetting adhesive 3c. Air expanded during heating and hardening is released to the outside from the hole 3d and when the whole part is cooled the protrusion 3b is irradiated with a light beam of a halogen lamp or the like to melt the apex portion of the protrusion 3b and a die 3e is stuck thereon.