PURPOSE: To seal closely to protect from insects like cockroach by providing an electric magnet in the space from an outer box under a container box and unlocking a locking device of an open spring so as to always push forward the container box.

CONSTITUTION: A plunger 26 is pulled toward an electric magnet 18 side and a locking lever 25 is rotated clockwise to unlock when a switch 19 is turned on. And hence, a container box 14 is pushed forward until flanges 40, 41 of holding guide plates 23, 24 contact the inner face of the container box 14 and further it is pulled forward with holding the periphery of a door 13. When the container box is contained by pushing the front face of the door 13 after water feed, the deep faces 42, 43 of the holding guide plates 23, 24 contact the deep face 44 of an inner box 10 and when still further pushing it, open springs 20, 21 are charged to hook by the locking lever 25. In this time, even if the door 13 is relieved from hands, the container 14 and the door 13 are not moved back and a packing 28 is securely sealed and protected from cockroaches and dusts.