To solve the problem that opening/closing of a lid has not been considered or it has been conducted using an air cylinder or ball screw which is not a simple means and two planes contacting an O-ring have not been designed so as to be parallel when pressing the O-ring.

The vacuum chamber includes a body 11 and a lid 12 and is sealed with an O-ring 15 located between the body 11 and the lid 12. The lid 12 is connected with the body 11 by an opening/closing means 14 at one end thereof and is equipped with a holder 13 for lifting the lid 12 at the other end thereof. The opening/closing means 14 is designed to ensure a parallel plane between the body 11 and the lid 12 when closing the lid 12 and to press the O-ring 15, holding the parallel plane when the body 11 is vacuumed.