A filtration apparatus having a cover pivotably installed through a hinge mechanism has a casing bracket secured to a casing flange and a cover bracket secured to the cover. A pin is inserted through insertion holes in side walls of the casing bracket and through insertion holes in side walls of the cover bracket. The filtration apparatus is provided with a stopper mechanism for maintaining the cover in a full-open position when it is fully opened, and also provided with a stopper-releasing mechanism for canceling the stopper function.