PURPOSE: To provide a method and device for constituting an underground closed construction with assistant from the ground level for preventing the pollution caused by dump.

CONSTITUTION: An underground closed construction to sufficiently enclose dump in downward and periphery parts is constituted of a longitudinally extending main tunnel 2 and at least one side tunnel connected to the side of the main tunnel 2 and extending to the ground level, and a filling material or further a sealing material unit and/or draining pipe unit depending on occasion is introduced into the side tunnel for safetying the dump. The side tunnel is constructed upward with one end part of the side tunnel connected to the main tunnel 2 and an upper end opening 4 reaching the ground level by means of an advancing device having an excavator, carrying device and expanding reinforcing machine. Rocks and earth excavated by the excavator are carried by the carrying device to the end part opened to the main tunnel 2 and further to the ground level, and at least the filling material for composing a closed construction is fed from the ground level opening 4.