Operating a strainer using centrifugal force generated by the rotation of a bottomed cylindrical vessel having filtering holes in a side surface. The strainer can eliminate the clogging of the filtering holes and maintain the optimal straining effect while maintaining the optimal pressure and duration of pressing food ingredients. The strainer catches a filtrate discharged through the filtering holes of the bottomed cylindrical vessel to the outside of the vessel while rotating the bottomed cylindrical vessel, which contains an object to be strained input therein, in a predetermined rotation direction at a first rotation speed, rotating the rotary pressers in the same rotation direction as the bottomed cylindrical vessel at a second rotation speed different from the first rotation speed of the bottomed cylindrical vessel by a predetermined speed difference.
