PURPOSE: To improve sealing function by providing a seal means sealing an annular part formed in a valve stem hole and a seal means having a cylindrical metallic bellows between the valve stem and a valve body.

CONSTITUTION: An annular seal 23 is provided in a proper annular groove of the end part of a cylindrical extended part, it is pressed by cover 20, and the liquid-tight and gas-tight seal is formed between the cover 20 and the valve body 12. A packing gland 58 compresses a packing assembly 55, and sealingly engages a valve stem 40 with a valve stem inducing cylinder 50. A metallic bellows 70 provides a liquid-tight and gas-tight valve stem seal to a valve having a rectilinearly moving valve system. In this way the sealing function is improved.