To provide a working method in a shielded working space which can secure a working space even when negative pressure is applied in the space on the side where work is performed, which is safe and can make materials, instruments or the like inexpensive.

The working method in a shielded working space consists of a process where a shielding layer 20 which shields the space 1 on the work side from an entry space 2 is attached in the peripheral edge part of the space 1 on the work side, a process where a bag-shaped layer 40 used for work which can be slid with respect to the shielding layer 20 is attached to the shielding layer 20, a process where a negative pressure is formed in the space 1 on the work side, a process where the bag-shaped layer 40 used for work is pushed out on the space 1 on the work side, and a process where the shielding layer 20 is drawn toward the entry space side 2 and a work space 1a is formed. The work in the work space 1a is performed while carrying out slide movement of the bag-shaped layer 40 used for work with respect to the shielding layer 20.