A hopper in which fragments of components generated due to vibration or fallen off bolts, nuts, and the like, can be prevented from being mixed into articles by a simplified arrangement. A link mechanism for opening/closing a gate is disposed on a plate provided on one side face of the housing (20) of a pool hopper (7). A cover (25) covering the entirety of the link mechanism is disposed such that the cover (25) can be fixed removably to the housing (20). A fixing/removing mechanism (62) slides in an elongated hole (64) made at the swelling part (63) of the cover body (61) in the direction of arrows (O, P). The fixing/removing mechanism (62) comprises a slide member (65), a fixing/removing operation member (66) on the outside of the cover body (61) coupled with the slide member (65) and an engaging member (67) on the inside thereof, and nuts (69a, 69b) on the plate side engaging with the engaging member (67).