1. A system for monitoring a molding machine when producing a sandmold contained in a flask by using the molding machine that includes a vertically-movable supporting frame installed across upper ends of frame-setting cylinders mounted on a machine base; a pattern carrier for carrying thereon a pattern plate to a place above a central part of the machine base; an annular leveling frame for surrounding the sides of the pattern plate and for vertical sliding; the flask to be placed on the leveling frame; a sand hopper suspended from the vertically-movable supporting frame, for holding molding sand therein, the sand hopper selectively having an air-ejecting chamber therein to eject an air-jet for aeration by which the molding sand is floated and fluidized; a plurality of squeeze feet disposed at the bottom of the sand hopper, the squeeze feet being controllable to vertically move and stop; sand-charging nozzles disposed around the squeeze feet, for introducing the molding sand from the sand hopper into the flask; a filling frame vertically movably connected to filling-frame cylinders, for surrounding the squeeze feet and the sand-charging nozzles from their outside and for being placed on the flask when moved downwardly; the system comprising: at least one sensor connected to the molding machine for detecting an attribute as required on the molding machine; a local unit connected to the sensor and a communication network, for receiving signals corresponding to the attribute detected by the sensor and sending the signals over the communication network; and a remote unit connected to the communication network, for monitoring the attribute by receiving the signals from the local unit, displaying values on the attribute, analyzing the attribute, and displaying the results of the analysis.