Spindle Structure

The present disclosure provides a spindle structure including a base, a spindle, a sliding member, a restoring mechanism, and a restriction member. The spindle is rotatably received in the base and forms a receiving room. An end of the receiving room is a blind 5 end communicating exterior via a gas channel. The sliding member is slidably received in the receiving room, and two ends thereof are a piston and a driving portion respectively. A gas cavity is defined between the piston and the blind end. The sliding member tends to move toward the blind end due to the restoring mechanism. The restriction member is connected to the driving portion and radially deforms when the sliding member slides so as 0 to fix or to release the tool-holder. The sliding member slides outward when the gas cavity is injected with gas via the gas channel.