Provided is an operation method for a strainer. With regard to a strainer that uses the centrifugal force generated by the rotation of a bottomed cylindrical vessel (3) that has filtering through-holes (3d) in a peripheral side surface, the method is capable of optimally maintaining straining action and of resolving the problem of the clogging of the filtration through-holes while still optimally maintaining the pressure and duration of the pressing force applied to a foodstuff. Also provided is an automatic strainer device. The present invention has: a vertical bottomed cylindrical vessel that is supported so as to be rotatable around a central axis and that has filtering through holes opened in a peripheral side plate rotating pressing elements (24, 25) that are on the inside of the bottomed cylindrical vessel and that are supported so as to be rotatable around the central axis while contacting or approaching the inner peripheral surface of the peripheral side plate and a filtered object collecting member that collects filtered objects that are expelled out of the bottomed cylindrical vessel from the through holes of the vessel. The present invention includes a step for rotating the bottomed cylindrical vessel, into which objects to be filtered are fed, in a prescribed rotation direction at a first rotation speed and for simultaneously rotating the rotating pressing elements in the same rotation direction as the bottomed cylindrical vessel at a second rotation speed that has a prescribed speed difference from the first rotation speed.Linvention concerne un procédé de fonctionnement pour une passoire. En ce qui concerne une passoire qui utilise la force centrifuge générée par la rotation dun récipient cylindrique à fond (3) qui a des trous traversants de filtration (3d) dans une surface latérale périphérique, le procédé permet de maintenir de façon optimale une action de filtration et de résoudre le problème dobstruction des trous traversants de filtration tout en
