To provide: an image forming agent storage container configured to facilitate the sealing of a discharge hole formed in a container body; an image forming apparatus; a method of mounting the image forming agent storage container; a method of detaching the image forming agent storage container; a method of filling an image forming agent; and a method of refilling the image forming agent.

The storage container 300 includes the container body 306 formed with the discharge hole 312 and a filling hole 314, an opening and closing part 350 opening and closing the discharge hole 312, a lid member 340 sealing the filling hole, and an operating member 380 having a facing portion 382 facing the filling hole 314 and used to operate the opening and closing part 350. The operating member 380 moves between a first position where the discharge hole 312 is brought into an opened state, a second position where the discharge hole 312 is brought into a closed state and the facing portion 382 is arranged at a position which overlaps the container body 306, and a third position where the discharge hole 312 is brought into a closed state and the facing portion 382 is arranged at a position which does not overlap the container body 306 in the direction of gravity.