A powder supplying device includes a powder container frame, a powder container detachably installable in the powder container frame horizontally and including a container body in which a discharge port through which powder is discharged from the container body is formed, a shutter member attached to the container body to open and close the discharge port by moving along the container body in a direction in which the powder container is installed, and at least one shutter control member movably attached to the powder container frame. The shutter control member opens and closes the shutter member by moving together with the powder container as the powder container is fitted into and pulled out from the powder container frame.