To automatically and safely regulate the pressure in a process even when the heating treatment is effected without taking any action in advance by storing a diaphragm valve in a receiving pan so that a pressing part is pressed against a recessed part of the receiving pan in a mutually airtight manner.

In a pressure regulating valve, a diaphragm valve 3 is stored in a receiving pan 2 so that a pressing part 31 of the diaphragm valve 3 is pressed against a recessed part 21 of the receiving pan 2 in a mutually airtight manner. In the receiving pan 2, a large number of fine through holes 22 are provided in the recessed part 21 of a center part, and a flange part 23 slightly expanded inward as necessary is provided on an upper edge of an opening. In the pressure regulating vale, when a silicone oil is interposed in a pressed part between the recessed part 21 of the receiving pan 2 and the pressing part 31 of the diaphragm valve 3, the airtightness is improved to minimize the degradation of a content during the storage of a packaged body.