PURPOSE: To treat safely and exactly slag by connecting a cylinder device to a pan rest fitted freely verticaly rotatably to supporting frames on a floor and specifying the height of the revolving shaft of the pan rest.

CONSTITUTION: A shaft 16 fixed to both end parts of a pan rest 10 and projects horizontally is freely rotatably built in bearings 17 fixed to the top end of two pieces a set of supporting frames 18 erected and fixed on a floor. The pan rest 10 has the shape in which the side parts and bottom part are closed. Said rest is connected to the end of the piston rod of a cylinder device 21 having the one end fixed to the frames 18, by means of the horizontal shaft 12a built in the bearings 12 fixed in the side parts. The hook of an overhead crane is hooked to the hook pin 6 of a casting pan 1, and the pan 1 is carried and is lowered into the perpendicularly held rest 10. The shaft 16 in this stage is so positioned as to be lower than the pin 6 and higher than the center of gravity of the pan 1. When the device 24 is contracted, the rest 10 rotates around the shaft 16 and slag is dischared from the pan 1.