SHIELD MACHINE

PROBLEM TO BE SOLVED: To provide a shield machine such that the work of replacing a cutter bit can be performed safely without hindrance by surely preventing water, earth and sand from entering the working chamber of a cutter spoke. SOLUTION: This shield machine has a working chamber 8 formed inside the cutter spoke 2-1 of a cutter head 2, so that a cutter bit can be replaceably attached to the cutter spoke 2-1 from the working chamber 8. The shield machine is provided with a central closed chamber 7-1 having an inner entrance 11a enabling compressed air to be supplied into the working chamber 8 and capable of being opened and closed by a closing device, an outer entrance which can be opened and closed by the closing device, and an internal space that allows passage therein, and a peripheral closed chamber 7-2. A center drum 2-3 rotatably installed at the center of the shield body 1 is communicated with the central closed chamber 7-1 and the working chamber 8, and the peripheral closed chamber 7-2 is longitudinally movably installed so that when moved forward, it can be hermetically communicated with the working chamber 8.