PURPOSE: To prevent the faulty replenishment of offset preventing liquid by moving a sucking tube in a tank where the preventing liquid is stored in a state where it follows the movement of liquid level and surely supplying the preventing liquid regardless of the amount of the preventing liquid in the tank.

CONSTITUTION: A pump 13 is provided between an offset preventing liquid sucking tube 14 and an offset preventing liquid supplying tube 6, and the sleeve 19 of the pump 13 is attached to a sleeve holding tool 12 fixed on the main body side of the device so that it can move up and down. A suspending member 7 is fixed to the tube 14. The tube 14 and the sleeve 19 integrally move up and down with the liquid level by means of the member 7 consisting of foaming styrene, etc. Furthermore, the distance of the tube 14 projecting downward from the lower surface of the member 7 is made smaller than a distance between the base surface of the tank and the liquid level detecting point of a liquid level detecting sensor 9 provided in a tank 8. Therefore, dust on the bottom of the tank is not sucked.