A structural strength of a bell jar is improved. The bell jar (10) is made of a quartz glass material which constitutes a chamber (110) of a vacuum processing apparatus (100) to perform a predetermined processing on an object to be processed by maintaining the chamber (100) at a negative pressure. The bell jar (10) comprises: a manipulation-type body (11) of which a lower end is opened; a flange portion (12) formed along the lower end of the body (11); a convex portion (13) formed on an upper portion higher than the flange portion (12) on a side surface (11a) of the body (11), and extending along a circumferential direction of the body (11).
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