To provide an apparatus housing mechanism which can house an apparatus for a rack without using a shelf board.

The apparatus housing mechanism comprises an engaging means for integrating a plurality of apparatus units U1, U2 detachably in a state where they are coupled each other on the side surfaces and arranged laterally. The plurality of apparatus units U1, U2 are coupled using a coupling part 8 consisting of two C-shaped members formed to fit each other, and then attached to posts 2, 3 in a rack 1. The plurality of apparatus units U1, U2 can be housed in the rack 1 without using a shelf board.