To provide a compact accommodation box for connection appliances such as a branch joint, a valve and an instrument installed midway of a double pipe used as a transport pipe of chemicals, etc., and a laying method therefor in which the piping work is easy.

This accommodation box for connection appliances is provided in an inner pipe of the double pipe, a side wall having a connection port through which an outer pipe can be passed in a sealable manner is fitted to both sides of a box body which can cover and accommodate the connection appliances connected to the inner pipe in an attachable/detachable manner. The side walls and the box are passed through the outer pipe, and after the connection appliances are connected to the inner pipe, the box and the side walls are moved.